Telescopically assembled mechanical connector

ABSTRACT

A telescopically assembled, Merlin™ Family Connector is provided with one or more sets of threads on substantially matching frustoconical surfaces of a pin and a box of the connector. Strengthening means are introduced involving at least one of: a mechanical stiffening clamp interacting with an outside surface of the box or a mechanical stiffening clamp interacting with an inside surface of the pin. The stiffening clamps may include systems of arbitrarily oriented ribs and/or fairing surfaces. The said strengthening means may be essentially annular clamps that would have relatively regular shapes essentially conforming to the external or internal surfaces of the box or the pin, respectively. The above modifications can be introduced to traditional connectors and to connectors designed to transfer high torsional loads.

This application is a Continuation in Part (CIP) application followingU.S. Utility patent application Ser. No. 17/485,336 titledTELESCOPICALLY ASSEMBLED MECHANICAL CONNECTOR filed on Sep. 25, 2021incorporated herein, which is a CIP application following U.S. Utilitypatent application Ser. No. 16/920,350 titled MECHANICAL CONNECTORSfiled on Jul. 2, 2020 issued on Oct. 26, 2021 as U.S. Pat. No.11,156,313 and incorporated herein, which followed a CIP applicationSer. No. 15/782,835 titled ENHANCEMENTS OF MECHANICAL CONNECTORTECHNOLOGY filed on Oct. 12, 2017 and incorporated herein, which was aCIP application following U.S. Utility patent application Ser. No.15/239,696 for MECHANICAL CONNECTOR OF LONG TORSIONAL AND BENDINGFATIGUE LIFE filed on Aug. 17, 2016 and incorporated herein, which isbased on U.S. provisional applications No. 62/189,437 filed on Jul. 7,2015 and on No. 62/148,665 filed on Apr. 16, 2015, and on PCTApplication PCT/US16/28033 (WO/2016/168,707) filed Apr. 18, 2016, U.S.provisional patent application No. 62/409,313 filed on Oct. 17, 2016introduces enhancements to mechanical connector technology. Thisapplication claims the benefits of priority related to U.S. provisionalapplications Ser. Nos. 62/148,665, 62/189,437 and 62/409,313, of PCTapplication PCT/US16/28033 (WO/2016/168,707), and of U.S. utility patentapplication Ser. Nos. 15/239,696, 15/782,835, 16/920,350 and 17/485,336.

TECHNICAL FIELD

This invention relates to mechanical connectors used in any engineeringapplication, and in particular in offshore engineering at or near thesea surface, above or below the water surface, as well as anywhere inthe water column.

BACKGROUND ART

Mechanical connectors of the Merlin™ group (featured for example inGB1,573,945, GB2,033,518, GB2,099,529, GB2,113,335, U.S. Pat. Nos.5,964,486, 8,056,940, EP0,803,637, etc.) and types derived by thirdparties from the Merlin™ group of designs are widely used in OffshoreEngineering. Merlin™ is a trade name of the most widely used connectorin the group that is manufactured by Oil States Industries. Similarconnectors acting on the same principle are also manufactured by others,but for simplicity all those designs are referred to herein as Merlin™group, or Merlin™ family connectors. Those designs and their advantagesare well known to anybody skilled in the art.

In particular, the Merlin™ group connectors known characterize with highstatic and fatigue strengths with regard to axial and bending loads, asrequired for traditional tendon, conductor, riser, etc. applications.The above traditional connectors do not typically experience high staticor fatigue torsional loads and their torsional load capacities arelimited to frictional resistance resulting from radial and axialconnector preload that could be augmented by the actual loading of theconnector. Accordingly the Merlin™ family connectors characterize withlimited torsional load capacities that may be difficult to controlaccurately by design means. In known connectors the box outside stressdiameters and the pin inside stress diameters are kept substantiallyconstant along the threaded segments of the said connectors. Minordepartures from that have been described in prior art literature, butthose are nowhere as pronounced as in novel connectors introducedherein. A background art mechanical connector is provided with a thread(zero pitch angle for background art connectors) on substantiallymatching frustoconical surfaces extending between two sets of (metal)nipple seals (annotation 140, see FIG. 2 ; note that (metal) nippleseals 140 use the same basic configuration and operation principle onbackground art connectors, as they do on novel connectors). One of thosesets of said (metal) nipple seals is located near an end of a box andthe other said set of said (metal) nipple seals is located near an endof a pin. It is known to anybody skilled in the art that each of theabove sets of the said (metal) nipple seals incorporates axiallyengaging, substantially cylindrical surfaces with an outside surface andan inside surface of a male substantially cylindrical segmentinteracting radially through the mechanism of a hoop stress withsubstantially matching surfaces of a substantially cylindrical cavity.

Oil States Industries offers also a high torsional capacity Lynxconnector, but that connector is structurally different and it is notdesigned with particularly high torsional fatigue strength in mind. TheLynx is designed to resist accidental high loads.

Important design considerations pertaining to selecting heights ofprotrusions and depths of grooves used in the Merlin™ family connectorsat various axial locations of those connectors, preferable taper anglesat various locations as well as means to improve the telescopic assemblyand disassembly operations with the use of hydraulic pressure aredisclosed for example in U.S. Pat. No. 8,056,940. Those design features,or their equivalents, can be optionally applied to these designs,wherever applicable.

DISCLOSURE OF INVENTION

This invention builds up on technical features and on the industryexperience with the use of Merlin™ family connectors. Novel technicalstructural features, not used previously in the Merlin™ familyconnectors, are provided in order to handle high torsional loads. Inaddition to friction, structural means that are used in order totransfer high torsional loads include: dog-clutch teeth, fitted pins,keys, splines and interlocked thread systems, all used in isolation orin arbitrary combinations. Modifications in the shapes of the box andthe pin are introduced. Those are useful for weight control. The abovecan be used in particular in connectors designed for lower designpressures and for smaller piping/tubing diameters than are those usedtypically subsea. Additionally a use of assembly/disassembly fluids thatsolidify in at least some ranges of operational temperatures ofconnectors is introduced. Those include in particular resins or tar-likenon-metals and liquid metals solidifying in single phases as well as inmultiple phases like for example binary, ternary etc. eutectics.

Merlin™ family connectors and some of their third party derivatives canbe welded to the ends of pipes to be connected, or the pins and theboxes forming the connections can be shaped in the actual pipe used.Typically high yield strength and high quality materials are used forbuilding Merlin™ family connectors, and the same or similarcharacteristics materials should be used for building connectorsaccording to this invention.

The following design enhancements of connectors are introduced herein:

-   -   modifications of shapes of boxes and/or pins for lower operating        pressures and assembly/disassembly pressures;    -   introduction of inside diameter (ID) fairings, outside diameter        (OD) fairings strengthening fins, planar, curved, box or        honeycomb stiffeners and web stiffeners for stiffness control,        buckling resistance, material saving and weight control;    -   modifications of thread tooth geometry that enhance leak        resistance & improve loading;    -   introduction of metallic and non-metallic assembly/disassembly        fluids that essentially solidify in the design ranges of        temperatures;    -   improvements in the solid to solid heat transfer between the pin        and the box and improvements in heat dissipation.

Static and fatigue bending load capacities of novel connectors remainhigh, while the axial load capacities may or may not be high, dependingon the design requirements. Depending on specific design requirementsand economic factors (like for example component cost and the size ofthe market expected) the engineer can select between two subgroups ofnovel connectors that feature:

-   -   Novel connectors adapting Merlin™ family connectors for        transferring high torque loads by adding high torque capacity        through optimized structural additions;    -   Novel connectors featuring structural elements that require        major design modifications.

The first subgroup includes:

-   -   Novel connectors utilizing fitted pins to transfer structurally        high torsional loads;    -   Novel connectors utilizing the dog-clutch principle to transfer        structurally high torsional loads;    -   Novel connectors utilizing the shaft-rotor type key systems to        transfer structurally high torsional loads.

The second subgroup includes:

-   -   Novel connectors utilizing the shaft-rotor spline connection        principle to transfer structurally high torsional loads.    -   Novel connectors utilizing the threaded connection principle to        transfer structurally high torsional loads.

Novel connectors belong to the said first subgroup may involve newdesigns or they may involve design modifications of known Merlin™ familyconnectors. The structural additions are introduced in the not veryhighly loaded regions of known connectors, or in regions where loadingpertaining to ‘traditional design loads’ on Merlin™ family connectorsare reduced. Retrofitting spare or retired known connectors with newstructural features and torque loading capabilities may be alsofeasible.

Novel connectors featuring the enhancements listed above can be built asnew, carefully optimized designs.

Novel connectors feature variable, including for example tapered designsof the outside (stress) diameters of connector boxes and variable,including for example tapered designs of the inside (stress) diametersof pins in order to extend the use of the Merlin™ family connectors foruse with smaller design pressures (and therefore reduced pressures usedfor the assembly and disassembly of connectors) in comparison with theMerlin™ family connectors that are typically used offshore. Tapering theOD makes the box shell more flexible and it also extends the use of theconnectors to sizes smaller than those typically used with Merlin™family connectors, i.e. 8⅝ inches (219.1 mm) and greater. Merlin™ familyconnectors used offshore are typically manufactured through the processof high precision, computer numerically controlled (CNC) single pointdiamond tool turning. The inside and outside stress diameters of aparticular cross-section of a pin or a box are herein those essentiallygoverning the hoop stressing of a given cross section of the pin or thebox, respectively. Anybody knowledgeable in the art knows that hoopstresses at any diameter inside a wall of a cylindrical section can beessentially expressed in terms of the pressure across the wall and theinside and outside (stress) diameters of that cylindrical section.

Other features facilitating the extending this connector technology andthe technology of the Merlin™ family connectors to smaller sizes involveincreasing the manufacturing accuracy (decreasing tolerances) byutilizing more accurate high precision manufacturing technology. Thatincludes for example using smaller, more accurate and/or more robustlybuilt lathes, grinding, polishing, electrochemical polishing,electrolytic polishing (electropolishing), tumbling, rumbling,barreling, vibratory finishing, burnishing, peening, laser peening,sandblasting, etc. that allow achieving a greater dimensional accuracythan does turning. 3-dimensional (3D) printing can also be used.

For applications where low weight of novel connectors (exampleaerospace) is of importance, it may be advisable to use smaller numbersof thread teeth and/or very ‘slim’ thread teeth profiles, even if thatmakes it impossible to make up connections without a use of apressurized fluid. The same can be utilized whenever the design lengthsavailable for tubing or piping are limited, which may require a use ofshort connector lengths and short overlapping segments between the boxand the pin.

Merlin™ family connectors, including those introduced herein areassembled and disassembled telescopically essentially in the same way,as described in the prior art documents. Assembled and/or disassembledtelescopically means herein undergoing telescopic assembly and/ordisassembly operations, respectively. The telescopic assembly and/ordisassembly operations of the prior art Merlin™ family connectors andessentially of those introduced herein are well known to those skilledin the art and are described in the prior art documents. During the saidtelescopic assembly and/or disassembly operations the main axes of thepins and the boxes essentially coincide during the said telescopicassembly and/or disassembly operations, while all points of the saidpins and/or boxes substantially follow essentially straight lines thatare essentially parallel to the said essentially coinciding axes of thesaid pins and/or the said boxes. It is understood in the abovesimplified definition of the telescopic assemblies and/or disassemblies(and by implication in the definitions of being assembled and/ordisassembled telescopically) that the term ‘essentially parallel’disregards for simplicity the modifications of the shapes of the saidstraight lines due to radial deformations of the pins and the boxesresulting from pushing the said boxes together during the assembliesand/or those due to the applications of assembly or disassembly fluidpressures (hoop strain and meridional bending). Accordingly, during thesaid telescopic assembly and/or disassembly operations the said boxesand pins undergo radial deformations essentially in their meridionalplanes and the relative trajectories of points of the said pins andboxes depart from being strictly parallel to the connector axis and aresaid to be ‘essentially parallel’ lines because of the hoop strain andthe meridional bending, as it is required by the said telescopicassembly and/or disassembly operations. That is well understood by thoseskilled in the art. Substantially no relative rotation of the boxesrelative the pins is required to carry out the said telescopic assemblyand/or disassembly operations, which distinguishes the Merlin™ familyconnectors from conventional pipeline connectors utilizing taperedthreads connected by screwing boxes and pins together, which is not takeplace during the said telescopic assemblies and/or disassemblies. No‘screwing together’ is required during the telescopic assemblies and/ordisassemblies of the Merlin™ family connectors. Accordingly, referringto connectors assembled and/or disassembled telescopically is hereinsynonymous with describing Merlin™ family connectors—those introducedherein, and their prior art predecessors.

This invention involves a telescopically assembled mechanical connectorprovided with a thread on substantially matching essentiallyfrustoconical surfaces of a box and a pin, said substantially matchingessentially frustoconical surfaces of said box and said pin extendingessentially between two sets of nipple seals, whereas one said set ofsaid nipple seals is located near an end of said box and another saidset of said nipple seals is located near an end of said pin and whereaseach said set of said nipple seals incorporates axially engaging,substantially cylindrical surfaces with an outside surface and an insidesurface of a male substantially cylindrical annular segment interactingradially through a mechanism of a hoop stress with substantiallymatching surfaces of a substantially cylindrical annular cavity, whereassaid sets of said nipple seals are used for sealing a cavity betweensaid box and said pin;

whereas said telescopically assembled mechanical connector is assembledand disassembled utilizing a pressure of an assembly/disassembly fluidwhich expands said box and contracts said pin in a radial direction,which enables an assembly stroke in an axial direction that makes up aconnection by engaging said threads of said box and said pin or whichenables a disassembly stroke along said axial direction by disengagingsaid threads of said box and said pin respectively; whereas said threadsof said box and said pin can engage only in a correct axial position dueto a use of a non-uniform axial spacing of said threads, and whereas anexcess of said assembly/disassembly fluid is removed through fluidoutlet ports;whereas:

-   -   said telescopically assembled is defined as being assembled in a        telescopic way,    -   being assembled in said telescopic way is defined as having all        points of said pin and/or said box substantially follow        essentially straight lines during an assembly, whereas said        straight lines are essentially parallel to essentially        coinciding axes of said pin and of said box;        whereas said telescopically assembled mechanical connector        includes an at least one mechanical clamp interacting        structurally with said box and/or said pin, while remaining        essentially unbonded to said box and/or said pin;        whereas said mechanical clamp interacting structurally with said        box essentially restricts structurally a shell of said box from        radial deformations outwards, i.e. away from an axis of said        telescopically assembled mechanical connector, and/or said        mechanical clamp interacting structurally with said pin        essentially restricts structurally a shell of said pin from        radial deformations inwards, i.e. towards said axis of said        telescopically assembled mechanical connector;        whereas said mechanical clamp stabilizes an essentially circular        shape of a cross-section of said telescopically assembled        mechanical connector by essentially stiffening structurally said        box and/or said pin, respectively;        whereas said mechanical clamp interacting structurally with said        box and/or said pin is installed after said box and said pin are        assembled telescopically and said excess of said        assembly/disassembly fluid is removed through said fluid outlet        ports and said mechanical clamp interacting structurally with        said box and/or said pin is removed before said disassembly        stroke is started;        wherein said telescopically assembled mechanical connector        includes at least one of:    -   said mechanical clamp essentially stiffening structurally an        outside surface of said box,    -   or said mechanical clamp essentially stiffening structurally an        inside surface of said pin.

This invention involves a mechanical connector, including atelescopically assembled mechanical connector, provided with a thread onsubstantially matching frustoconical surfaces of a box and a pin, saidsubstantially matching frustoconical surfaces of said box and said pinextending essentially between two sets of (metal) nipple seals, whereasone said set of said (metal) nipple seals is located near an end of saidbox and another said set of said (metal) nipple seals is located near anend of said pin and whereas each said set of said (metal) nipple sealsincorporates axially engaging, substantially cylindrical surfaces withan outside surface and an inside surface of a male substantiallycylindrical segment interacting radially through a mechanism of a hoopstress with substantially matching surfaces of a substantiallycylindrical cavity; whereas said sets of said (metal) nipple seals areused for sealing a cavity between said box and said pin that can bepressurized with an assembly/disassembly fluid in order to facilitate anassembly or a disassembly by radially expanding said box and radiallycontracting said pin; said mechanical connector, including saidtelescopically assembled mechanical connector, provided with said threadon said substantially matching frustoconical surfaces extendingessentially between said two sets of said (metal) nipple sealscharacterizes with a provision of a structural arrangement designed totransfer torque between said box and said pin of said mechanicalconnector, including said telescopically assembled mechanical connector,provided with said thread on said substantially matching frustoconicalsurfaces extending essentially between said two sets of said (metal)nipple seals;

wherein said structural arrangement designed to transfer torque betweensaid box and said pin of said mechanical connector, including saidtelescopically assembled mechanical connector, provided with said threadon said substantially matching frustoconical surfaces of said box andsaid pin includes at least one of:

-   -   a plurality of spline teeth,    -   a plurality of dog-clutch teeth, including a single dog-clutch        tooth,    -   a plurality of fitted pins, including a single fitted pin,    -   a plurality of keys,    -   a plurality of right-handed threads, including a single        right-handed thread, interlocking substantially with said thread        on said substantially matching frustoconical surfaces of said        box and said pin through the mechanism of at least one of:        -   an interlocking of said right-handed thread with said thread            on said substantially matching frustoconical surfaces of            said box and said pin having a zero-pitch angle,        -   an interlocking of said right-handed thread with said thread            on said substantially matching frustoconical surfaces of            said box and said pin having a left-handed thread,        -   an interlocking of said right-handed thread with said thread            on said substantially matching frustoconical surfaces of            said box and said pin having a right-handed thread with a            differing pitch,    -   a plurality of left-handed threads, including a single        left-handed thread, interlocking substantially with said thread        on said substantially matching frustoconical surfaces of said        box and said pin through the mechanism of at least one of:        -   an interlocking of said left-handed thread with said thread            on said substantially matching frustoconical surfaces of            said box and said pin having said zero-pitch angle,        -   an interlocking of said left-handed thread with said thread            on said substantially matching frustoconical surfaces of            said box and said pin having a right-handed thread,        -   an interlocking of said left-handed thread with said thread            on said substantially matching frustoconical surfaces of            said box and said pin having a left-handed thread with a            differing pitch;            whereas said structural arrangements designed to transfer            torque between said box and said pin are arranged            individually or in combinations in said mechanical            connector, including said telescopically assembled            mechanical connector, provided with said thread on said            substantially matching frustoconical surfaces of said box            and said pin.

This invention involves a mechanical connector, including atelescopically assembled mechanical connector, provided with a thread onsubstantially matching frustoconical surfaces of a box and a pin, saidsubstantially matching frustoconical surfaces of said box and said pinextending essentially between two sets of (metal) nipple seals, whereasone said set of said (metal) nipple seals is located near an end of saidbox and another said set of said (metal) nipple seals is located near anend of said pin and whereas each said set of said (metal) nipple sealsincorporates axially engaging, substantially cylindrical surfaces withan outside surface and an inside surface of a male substantiallycylindrical segment interacting radially through a mechanism of a hoopstress with substantially matching surfaces of a substantiallycylindrical cavity; whereas said sets of said (metal) nipple seals areused for sealing a cavity between said box and said pin that can bepressurized with an assembly/disassembly fluid that can be utilized inorder to facilitate an assembly and/or a disassembly by radiallyexpanding said box and radially contracting said pin; said mechanicalconnector, including said telescopically assembled mechanical connector,provided with said thread on said substantially matching frustoconicalsurfaces extending essentially between said two sets of said (metal)nipple seals being characterized with design modifications introduced inorder to control weight, stiffness and buckling resistance incorporatesat least one of:

-   -   an outside (stress) diameter of said box of said mechanical        connector, including said telescopically assembled mechanical        connector, provided with said thread on said substantially        matching frustoconical surfaces of said box and said pin        incorporating a plurality of tapering surfaces or their        approximation, including a single tapering surface or its        approximation,    -   or an inside (stress) diameters of said pin of said mechanical        connector, including said telescopically assembled mechanical        connector, provided with said thread on said substantially        matching frustoconical surfaces of said box and said pin        incorporating a plurality of tapering surfaces or their        approximation, including a single tapering surface or its        approximation.

This invention involves a mechanical connector, including atelescopically assembled mechanical connector provided with a thread onsubstantially matching frustoconical surfaces of a box and a pin, saidsubstantially matching frustoconical surfaces of said box and said pinextending essentially between two sets of (metal) nipple seals, whereasone said set of said (metal) nipple seals is located near an end of saidbox and another said set of said (metal) nipple seals is located near anend of said pin and whereas each said set of said (metal) nipple sealsincorporates axially engaging, substantially cylindrical surfaces withan outside surface and an inside surface of a male substantiallycylindrical segment interacting radially through a mechanism of a hoopstress with substantially matching surfaces of a substantiallycylindrical cavity; whereas said sets of said (metal) nipple seals areused for sealing a cavity between said box and said pin that can bepressurized with an assembly/disassembly fluid that can be used in orderto facilitate an assembly and/or a disassembly by radially expandingsaid box and radially contracting said pin;

wherein said telescopically assembled mechanical connector provided withsaid thread on substantially matching essentially frustoconical surfacesof said box and said pin includes strengthening means involving at leastone of:

-   -   a mechanical stiffening arrangement on an outside surface of        said box,    -   or a mechanical stiffening arrangement on an inside surface of        said pin.

The mechanical stiffening arrangements in the paragraph above may bemade of at least one of:

-   -   a high strength steel,    -   or a corrosion resistant alloy,    -   or a titanium alloy,    -   or an aluminum alloy,    -   or a magnesium alloy,    -   or a nickel based alloy,    -   or a non-metallic material including a plastic material,    -   or a non-metallic natural or a non-metallic synthetic material,    -   or an essentially composite material,    -   or an essentially elastomeric material,    -   or a material behaving in an essentially hyperelastic way,    -   or at least one of said box or said pin utilizes at least one of        a lining or a cladding or a weld overlay.        The non-metallic material, including plastic or/and hyperelastic        material may be fiber, wire, fiber-mesh or wire-mesh reinforced.        These mechanical stiffening arrangements may be integral with        the box or the pin, or they can be separate external/internal        strengthening arrangements, as applicable. In particular they        can be essentially annular clamps that would have relatively        regular shapes essentially conforming to the external or        internal surfaces of the box or the pin, respectively.

This invention involves a mechanical connector, including atelescopically assembled mechanical connector, provided with a thread onsubstantially matching frustoconical surfaces of a box and a pin, saidsubstantially matching frustoconical surfaces of said box and said pinextending essentially between two sets of (metal) nipple seals, whereasone said set of said (metal) nipple seals is located near an end of saidbox and another said set of said (metal) nipple seals is located near anend of said pin and whereas each said set of said (metal) nipple sealsincorporates axially engaging, substantially cylindrical surfaces withan outside surface and an inside surface of a male substantiallycylindrical segment interacting radially through a mechanism of a hoopstress with substantially matching surfaces of a substantiallycylindrical cavity; whereas said sets of said (metal) nipple seals areused for sealing a cavity between said box and said pin that can bepressurized with an assembly/disassembly fluid that can be used in orderto facilitate an assembly and/or a disassembly by radially expandingsaid box and radially contracting said pin;

wherein said mechanical connector, including said telescopicallyassembled mechanical connector, provided with said thread on saidsubstantially matching frustoconical surfaces extending essentiallybetween said two sets of said (metal) nipple seals being characterizedwith design modifications introduced in order to control weight,stiffness and buckling resistance incorporates at least one of:

-   -   an outside (stress) diameter of said box of said mechanical        connector, including said telescopically assembled mechanical        connector, provided with said thread on said substantially        matching frustoconical surfaces of said box and said pin is        provided with a plurality of stiffener fins, including a single        stiffener fin;    -   or an inside (stress) diameters of said pin of said mechanical        connector, including said telescopically assembled mechanical        connector, provided with said thread on said substantially        matching frustoconical surfaces of said box and said pin is        provided with a plurality of stiffener fins, including a single        stiffener fin.

This invention involves a mechanical connector, including atelescopically assembled mechanical connector, provided with a thread onsubstantially matching essentially frustoconical surfaces of a box and apin, said substantially matching essentially frustoconical surfaces ofsaid box and said pin extending essentially between two sets of (metal)nipple seals, whereas one said set of said (metal) nipple seals islocated near an end of said box and another said set of said (metal)nipple seals is located near an end of said pin and whereas each saidset of said (metal) nipple seals incorporates axially engaging,substantially cylindrical surfaces with an outside surface and an insidesurface of a male substantially cylindrical, annular segment interactingradially through a mechanism of a hoop stress with substantiallymatching surfaces of a substantially cylindrical, annular cavity;whereas said sets of said (metal) nipple seals are used for sealing acavity between said box and said pin that can be pressurized with anassembly/disassembly fluid that can be used in order to facilitate anassembly and/or a disassembly by radially expanding said box andradially contracting said pin;

wherein generatrices of interacting threads on said box and on said pinmismatch by design by at least 0.02°.

This invention involves a mechanical connector, including atelescopically assembled mechanical connector provided with a thread onsubstantially matching frustoconical surfaces of a box and a pin, saidsubstantially matching frustoconical surfaces of said box and said pinextending essentially between two sets of (metal) nipple seals, whereasone said set of said (metal) nipple seals is located near an end of saidbox and another said set of said (metal) nipple seals is located near anend of said pin and whereas each said set of said (metal) nipple sealsincorporates axially engaging, substantially cylindrical surfaces withan outside surface and an inside surface of a male substantiallycylindrical segment interacting radially through a mechanism of a hoopstress with substantially matching surfaces of a substantiallycylindrical cavity; whereas said sets of said (metal) nipple seals areused for sealing a cavity between said box and said pin that can bepressurized with an assembly/disassembly fluid that can be used in orderto facilitate an assembly and/or a disassembly by radially expandingsaid box and radially contracting said pin;

whereas:

-   -   loaded sides of said thread on said substantially matching        frustoconical surfaces of said box and said pin are defined as        sides, an engagement of which prevents a disconnection of said        telescopically assembled mechanical connector provided with said        thread on said substantially matching frustoconical surfaces of        said box and said pin,    -   unloaded sides of said thread on said substantially matching        frustoconical surfaces of said box and said pin are defined as        those sides of said thread on said substantially matching        frustoconical surfaces of said box and said pin that are not        said loaded sides of said thread on said substantially matching        frustoconical surfaces of said box and said pin,    -   each of thread generatrix angles θ1_(b), θ2_(b), θ1_(p), θ2_(p)        is measured between a normal to an axis of said box or between a        normal to an axis of said pin and a thread generatrix of said        unloaded side of said thread on said substantially matching        frustoconical surfaces of said box and said pin or of said        loaded side of said thread on said substantially matching        frustoconical surfaces of said box and said pin corresponding        respectively:        -   a box thread generatrix angle θ1_(b) is measured on said            unloaded side of said thread on said substantially matching            frustoconical surface of said box,        -   a box thread generatrix angle θ2_(b) is measured on said            loaded side of said thread on said substantially matching            frustoconical surface of said box,        -   a pin thread generatrix angle θ1_(p) is measured on said            unloaded side of said thread on said substantially matching            frustoconical surface of said pin,        -   a pin thread generatrix angle θ2_(p) is measured on said            loaded side of said thread on said substantially matching            frustoconical surface of said pin;            wherein said mechanical connector, including said            telescopically assembled mechanical connector, provided with            said thread on said substantially matching frustoconical            surfaces of said box and said pin is characterized by at            least one of absolute values of:    -   a thread generatrix mismatch angle |θ1_(b)−θ1_(p)|≥0.02°,    -   or a thread generatrix mismatch angle |θ2_(b)−θ2_(p)|≥0.02°.

This invention utilizes pressurized fluids that solidify in operationalconditions (including liquid metals and metallic alloys) and thosefluids are typically liquid, including molten, in order to assemble ordisassemble Merlin™ family connectors and/or mechanical connectors oflong torsional and bending fatigue life.

This invention involves also the use of pressurized fluids that solidifyin operational conditions (including liquid metals and metallic alloys)and those fluids are typically liquid, including molten, in order toassemble or disassemble mechanical connectors, including telescopicallyassembled mechanical connectors and/or mechanical connectors of longtorsional and bending fatigue life.

This invention involves a mechanical connector, including atelescopically assembled mechanical connector, provided with a thread onsubstantially matching frustoconical surfaces of a box and a pin, saidsubstantially matching frustoconical surfaces of said box and said pinextending essentially between two sets of (metal) nipple seals, whereasone said set of said (metal) nipple seals is located near an end of abox and another said set of said (metal) nipple seals is located near anend of a pin and whereas each said set of said (metal) nipple sealsincorporates axially engaging, substantially cylindrical surfaces withan outside surface and an inside surface of a male substantiallycylindrical segment interacting radially through a mechanism of a hoopstress with substantially matching surfaces of a substantiallycylindrical cavity; whereas said sets of said (metal) nipple seals areused for sealing a cavity between said box and said pin that can bepressurized with an assembly/disassembly fluid in order to facilitate anassembly and/or a disassembly by radially expanding said box andradially contracting said pin;

and wherein said mechanical connector, including said telescopicallyassembled mechanical connector, provided with said thread on saidsubstantially matching frustoconical surfaces extending essentiallybetween said two sets of said (metal) nipple seals includes anassembly/disassembly fluid remaining liquid, including molten, duringassembly/disassembly operations;and whereas after an assembly operation said assembly/disassembly fluidis allowed to solidify in an assembled condition of said mechanicalconnector, including said telescopically assembled mechanical connector,and remains essentially solid, thus becoming essentially a solid seal.

This invention involves a mechanical connector, including atelescopically assembled mechanical connector provided with a thread onsubstantially matching frustoconical surfaces of a box and a pin, saidsubstantially matching frustoconical surfaces of said box and said pinextending essentially between two sets of nipple seals, whereas one saidset of said nipple seals is located near an end of a box and anothersaid set of said nipple seals is located near an end of a pin andwhereas each said set of said nipple seals incorporates axiallyengaging, substantially cylindrical surfaces with an outside surface andan inside surface of a male substantially cylindrical segmentinteracting radially through a mechanism of a hoop stress withsubstantially matching surfaces of a substantially cylindrical cavity;whereas said sets of said nipple seals are used for sealing a cavitybetween said box and said pin that can be pressurized with anassembly/disassembly fluid in order to facilitate an assembly and/or adisassembly by radially expanding said box and radially contracting saidpin;

and whereas said mechanical connector, including said telescopicallyassembled mechanical connector, provided with said thread on saidsubstantially matching frustoconical surfaces extending essentiallybetween said two sets of said nipple seals includes saidassembly/disassembly fluid remaining liquid, including molten, duringassembly/disassembly operations;wherein after an assembly operation said assembly/disassembly fluid isallowed to solidify in an assembled condition of said mechanicalconnector, including said telescopically assembled mechanical connector,and remain essentially solid, thus becoming essentially a solid seal.

This invention involves a mechanical connector provided with a thread onsubstantially matching frustoconical surfaces of a box and a pin, saidsubstantially matching frustoconical surfaces of said box and said pinextending essentially between two sets of nipple seals, whereas one saidset of said nipple seals is located near an end of said box and anothersaid set of said nipple seals is located near an end of said pin andwhereas each said set of said nipple seals incorporates axiallyengaging, substantially cylindrical surfaces with an outside surface andan inside surface of a male substantially cylindrical segmentinteracting radially through a mechanism of a hoop stress withsubstantially matching surfaces of a substantially cylindrical cavity;whereas said sets of said nipple seals are used for sealing a cavitybetween said box and said pin;

whereas:

-   -   loaded sides of said thread on said substantially matching        frustoconical surfaces of said box and said pin are defined as        sides, an engagement of which prevents a disconnection of said        mechanical connector provided with said thread on said        substantially matching frustoconical surfaces of said box and        said pin,    -   unloaded sides of said thread on said substantially matching        frustoconical surfaces of said box and said pin are defined as        those sides of said thread on said substantially matching        frustoconical surfaces of said box and said pin that are not        said loaded sides of said thread on said substantially matching        frustoconical surfaces of said box and said pin,    -   each of thread generatrix angles θ1_(b), θ2_(b), θ1_(p), θ2_(p)        is measured between a normal to an axis of said box or between a        normal to an axis of said pin and a thread generatrix of said        unloaded side of said thread on said substantially matching        frustoconical surfaces of said box and said pin or of said        loaded side of said thread on said substantially matching        frustoconical surfaces of said box and said pin corresponding        respectively:        -   a box thread generatrix angle θ1_(b) is measured on said            unloaded side of said thread on said substantially matching            frustoconical surface of said box,        -   a box thread generatrix angle θ2_(b) is measured on said            loaded side of said thread on said substantially matching            frustoconical surface of said box,        -   a pin thread generatrix angle θ1_(p) is measured on said            unloaded side of said thread on said substantially matching            frustoconical surface of said pin,        -   a pin thread generatrix angle θ2_(p) is measured on said            loaded side of said thread on said substantially matching            frustoconical surface of said pin;            wherein said mechanical connector provided with said thread            on said substantially matching frustoconical surfaces of            said box and said pin is characterized by at least one of            absolute values of:    -   a thread generatrix mismatch angle |θ1_(b)−θ1_(p)|≥0.02°,    -   or a thread generatrix mismatch angle |θ2_(b)−θ2_(p)|≥0.02°.

This invention involves a mechanical connector provided with a thread onsubstantially matching frustoconical surfaces of a box and a pin,whereas at least one of said box or said pin utilizes friction welding.

This invention involves a mechanical connector provided with a thread onsubstantially matching frustoconical surfaces of a box and a pin,whereas at least one of said box or said pin is manufactured involvinginjection molding.

This invention involves a mechanical connector provided with a thread onsubstantially matching frustoconical surfaces of a box and a pin,whereas at least one of said box or said pin is manufactured involving3-Dimensional printing.

This invention involves a mechanical connector provided with a thread onsubstantially matching frustoconical surfaces of a box and a pin,whereas at least one of said box or said pin utilizes traditionalwelding fabrication.

This invention involves a mechanical connector provided with a thread onsubstantially matching frustoconical surfaces of a box and a pin,whereas at least one of said box or said pin is made of at least one of:

-   -   a high strength steel,    -   or a corrosion resistant alloy,    -   or a titanium alloy,    -   or an aluminum alloy,    -   or a magnesium alloy,    -   or a nickel based alloy,    -   or a non-metallic material including a plastic material,    -   or an essentially hyperelastic material,    -   or at least one of said box or said pin utilizes at least one of        a lining or a cladding or a weld overlay.        The non-metallic material, including plastic or/and hyperelastic        material may be fiber, wire, fiber-mesh or wire-mesh reinforced.

This invention involves a mechanical connector provided with a thread onsubstantially matching frustoconical surfaces of a box and a pin, saidsubstantially matching frustoconical surfaces of said box and said pinextending essentially between two sets of nipple seals, whereas one saidset of said nipple seals is located near an end of said box and anothersaid set of said nipple seals is located near an end of said pin andwhereas each said set of said nipple seals incorporates axiallyengaging, substantially cylindrical surfaces with an outside surface andan inside surface of a male substantially cylindrical segmentinteracting radially through a mechanism of a hoop stress withsubstantially matching surfaces of a substantially cylindrical cavity;whereas said sets of said nipple seals are used for sealing a cavitybetween said box and said pin;

wherein said mechanical connector includes an assembly/disassembly fluidremaining liquid during an assembly operation;and whereas after said assembly operation said assembly/disassemblyfluid is allowed to solidify in an assembled condition of saidmechanical connector, and remains essentially solid, thus becomingessentially a solid seal.

This invention involves a mechanical connector provided with a thread onsubstantially matching frustoconical surfaces of a box and a pin,wherein an assembly/disassembly fluid is metallic.

This invention involves a mechanical connector provided with a thread onsubstantially matching frustoconical surfaces of a box and a pin,wherein an assembly/disassembly fluid is non-metallic.

This invention involves a mechanical connector provided with a thread onsubstantially matching frustoconical surfaces of a box and a pin, saidsubstantially matching frustoconical surfaces of said box and said pinextending essentially between two sets of nipple seals, whereas one saidset of said nipple seals is located near an end of said box and anothersaid set of said nipple seals is located near an end of said pin andwhereas each said set of said nipple seals incorporates axiallyengaging, substantially cylindrical surfaces with an outside surface andan inside surface of a male substantially cylindrical segmentinteracting radially through a mechanism of a hoop stress withsubstantially matching surfaces of a substantially cylindrical cavity;whereas said sets of said nipple seals are used for sealing a cavitybetween said box and said pin; whereas said mechanical connector istelescopically assembled, and whereas the thread on the substantiallymatching frustoconical surfaces of the box and the pin includes at leastone of:

-   -   an axisymmetric thread,    -   a left-handed thread,    -   a right-handed thread;        and wherein said mechanical connector includes a plurality of        splines designed to transfer torsional loads structurally.

This invention involves a mechanical connector provided with a thread onsubstantially matching frustoconical surfaces of a box and a pin, saidsubstantially matching frustoconical surfaces of said box and said pinextending essentially between two sets of nipple seals, whereas one saidset of said nipple seals is located near an end of said box and anothersaid set of said nipple seals is located near an end of said pin andwhereas each said set of said nipple seals incorporates axiallyengaging, substantially cylindrical surfaces with an outside surface andan inside surface of a male substantially cylindrical segmentinteracting radially through a mechanism of a hoop stress withsubstantially matching surfaces of a substantially cylindrical cavity;whereas said sets of said nipple seals are used for sealing a cavitybetween said box and said pin;

whereas said mechanical connector is telescopically assembled, andwhereas the thread on the substantially matching frustoconical surfacesof the box and the pin includes at least one of:

-   -   an axisymmetric thread,    -   a left-handed thread,    -   a right-handed thread;        and wherein said mechanical connector includes a plurality of        keys designed to transfer torsional loads structurally.

This invention involves a mechanical connector provided with a thread onsubstantially matching frustoconical surfaces of a box and a pin, saidsubstantially matching frustoconical surfaces of said box and said pinextending essentially between two sets of nipple seals, whereas one saidset of said nipple seals is located near an end of said box and anothersaid set of said nipple seals is located near an end of said pin andwhereas each said set of said nipple seals incorporates axiallyengaging, substantially cylindrical surfaces with an outside surface andan inside surface of a male substantially cylindrical segmentinteracting radially through a mechanism of a hoop stress withsubstantially matching surfaces of a substantially cylindrical cavity;whereas said sets of said nipple seals are used for sealing a cavitybetween said box and said pin; whereas said mechanical connector istelescopically assembled, and whereas the thread on the substantiallymatching frustoconical surfaces of the box and the pin includes at leastone of:

-   -   an axisymmetric thread,    -   a left-handed thread,    -   a right-handed thread;        and wherein said mechanical connector includes a plurality of        fitted shear pins designed to transfer torsional loads        structurally.

This invention involves a mechanical connector provided with a thread onsubstantially matching frustoconical surfaces of a box and a pin, saidsubstantially matching frustoconical surfaces of said box and said pinextending essentially between two sets of nipple seals, whereas one saidset of said nipple seals is located near an end of said box and anothersaid set of said nipple seals is located near an end of said pin andwhereas each said set of said nipple seals incorporates axiallyengaging, substantially cylindrical surfaces with an outside surface andan inside surface of a male substantially cylindrical segmentinteracting radially through a mechanism of a hoop stress withsubstantially matching surfaces of a substantially cylindrical cavity;whereas said sets of said nipple seals are used for sealing a cavitybetween said box and said pin;

whereas said mechanical connector is telescopically assembled, andwhereas the thread on the substantially matching frustoconical surfacesof the box and the pin includes at least one of:

-   -   an axisymmetric thread,    -   a left-handed thread,    -   a right-handed thread;        and wherein said mechanical connector includes a one or more        dog-clutch teeth designed to transfer torsional loads        structurally.

This invention involves a mechanical connector provided with a thread onsubstantially matching frustoconical surfaces of a box and a pin, saidsubstantially matching frustoconical surfaces of said box and said pinextending essentially between two sets of nipple seals, whereas one saidset of said nipple seals is located near an end of said box and anothersaid set of said nipple seals is located near an end of said pin andwhereas each said set of said nipple seals incorporates axiallyengaging, substantially cylindrical surfaces with an outside surface andan inside surface of a male substantially cylindrical segmentinteracting radially through a mechanism of a hoop stress withsubstantially matching surfaces of a substantially cylindrical cavity;whereas said sets of said nipple seals are used for sealing a cavitybetween said box and said pin;

whereas said mechanical connector is telescopically assembled, andwhereas the thread on the substantially matching frustoconical surfacesof the box and the pin includes at least one of:

-   -   an axisymmetric thread,    -   a left-handed thread,    -   a right-handed thread,        and wherein said thread includes at least one of:    -   said left-handed thread interlocking with said right-handed        thread,    -   said axisymmetric thread interlocking with said left-handed        thread,    -   said axisymmetric thread interlocking with said right-handed        thread,    -   said left-handed thread interlocking with a left-handed thread        having a different pitch,    -   said right-handed thread interlocking with a right-handed thread        having a different pitch,        designed to transfer torsional loads structurally.

Depending on specific design requirements and economic factors (like forexample component cost and the size of the market expected) the engineercan select between two subgroups of novel connectors that feature:

-   -   Novel connectors adapting Merlin™ family connectors for        transferring high torque loads by adding high torque capacity        through optimized structural additions;    -   Novel connectors featuring structural elements that require        major design modifications.

The first subgroup includes:

-   -   Novel connectors utilizing fitted pins to transfer structurally        high torsional loads;    -   Novel connectors utilizing the dog-clutch principle to transfer        structurally high torsional loads;    -   Novel connectors utilizing the shaft-rotor type key systems to        transfer structurally high torsional loads.

The second subgroup includes:

-   -   Novel connectors utilizing the shaft-rotor spline connection        principle to transfer structurally high torsional loads.    -   Novel connectors utilizing the threaded connection principle to        transfer structurally high torsional loads.

Novel connectors belonging to the said first subgroup may include newdesigns or they may involve design modifications of known Merlin™ familyconnectors. The structural additions are introduced in the not veryhighly loaded regions of known connectors, or in regions where loadingpertaining to ‘traditional design loads’ on Merlin™ family connectorsare reduced. Retrofitting spare or retired known connectors with newstructural features and torque loading capabilities may be alsofeasible.

Novel connectors belonging to the said second subgroup require newdesign.

This invention involves a mechanical connector, including atelescopically assembled mechanical connector, whereas a connectionbetween a pin and a box of said mechanical connector is effected by theprinciple of zero-pitch angle threads provided on an essentially outsidesurface of said pin interacting axially and radially by means of axialand radial pretensions with essentially matching zero-pitch anglethreads provided on an essentially inside surface of said box; whereassaid zero-pitch angle threads provided on said essentially outsidesurface of said pin and said essentially matching zero-pitch anglethreads provided on said essentially inside surface of said box arearranged along a frustoconical pitch diameter surface that isessentially common to said essentially outside surface of said pin andto said essentially inside surface of said box; said mechanicalconnector being provided with structural means for transferring torquebetween said pin and said box, whereas said mechanical connector hasstatic and fatigue torsional and bending load capacities controlled bydesign means and said mechanical connector is also capable oftransferring axial loads between said pin and said box of saidmechanical connector;

said structural means for transferring torque between said pin and saidbox including:

-   -   a plurality of sets of splines provided on a plurality of        essentially matching surface sets of interactions between said        pin and said box, including a single essentially matching        surface set of interaction between said pin and said box; and        also including    -   a plurality of dog-clutch type teeth provided on a plurality of        essentially matching surface sets of interactions between said        pin and said box, including a single essentially matching        surface set of interaction between said pin and said box; and        also including    -   a plurality of fitted pins, including a single fitted pin,        whereas said plurality of said fitted pins is arranged along a        plurality of essentially matching surface sets between said pin        and set box, including a single essentially matching interaction        surface set between said pin and said box, whereas the transfer        of said torque is effected by interactions of said pin with said        plurality of said fitted pins and at the same time by an        interaction of said plurality of said fitted pins with said box;        and also including    -   a plurality of keys, including a single key, whereas said        plurality of said keys is arranged along a plurality of        essentially matching surface sets between said pin and set box,        including a single essentially matching surface set between said        pin and said box, whereas the transfer of said torque is        effected by interactions of said pin with said plurality of said        keys and at the same time by an interaction of said plurality of        said keys with said box; and also including    -   right-handed threads provided on a plurality of essentially        matching surface sets of interactions between said pin and said        box, including a single essentially matching surface set of        interaction between said pin and said box; and also including    -   left-handed threads provided on a plurality of essentially        matching surface sets of interactions between said pin and said        box, including a single essentially matching surface set of        interaction between said pin and said box; and also including    -   right-handed threads and left-handed threads provided on a        plurality of essentially matching surface sets of interactions        between said pin and said box, including a single essentially        matching surface set of interaction between said pin and said        box.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1 through 20 are provided to facilitate understanding of keyfeatures and key implementations of novel connectors.

FIG. 1 shows an exploded view of a novel connector utilizing splinetorque transfer.

FIG. 2 shows a cross-section through one side of a novel connectorutilizing spline torque transfer (shown in FIG. 1 ).

FIG. 3 presents a half view of a novel connector featuring a key torquetransfer arrangement.

FIG. 4 shows a detail of a key interacting with a box of a novelconnector.

FIG. 5 presents a half view of a novel connector featuring fitted pintorque transfer arrangement.

FIG. 6 shows details of fitted pins interacting with pins and boxes ofnovel connectors, one for each end of the interacting surfaces.

FIG. 7 depicts a detail of a novel connector assembled, whereas thedog-clutch torque transfer principle is utilized near the outsidesurfaces of the pin and the box. The dog-clutch teeth utilize the fullmaterial thickness available between the (metal) nipple seal region andthe outside surface of the connector.

FIG. 8 depicts a detail of a novel connector in an exploded view,whereas the dog-clutch torque transfer principle is utilized near theoutside surfaces of the pin and the box. The dog-clutch teeth utilize apart of the material thickness available between the (metal) nipple sealregion and the outside surface of the connector.

FIG. 9 depicts a detail of a novel connector assembled, whereas thedog-clutch torque transfer principle is utilized near the insidesurfaces of the pin and the box. The dog-clutch teeth utilize the fullmaterial thickness available between the (metal) nipple seal region andthe inside surface of the connector.

FIG. 10 depicts a detail of a novel connector in an exploded view,whereas the dog-clutch torque transfer principle is utilized near theinside surfaces of the pin and the box. The dog-clutch teeth utilize apart of the material thickness available between the (metal) nipple sealregion and the inside surface of the connector.

FIGS. 11 a through 11 z depict examples of schematic representations ofmany design implementations of novel connectors, most of which utilizethe following arrangements for transferring torque structurally:

-   -   the spline connection principle;    -   the key connection principle;    -   the fitted (shear) pin connection principle;    -   the dog-clutch connection principle;    -   the interlocking threads connection principle.

FIGS. 11 a through 11 y depict for the sake of example designimplementations of the above listed torque transfer mechanisms usedseparately and in combinations. Variations in structural segmentsequencing along the example connectors shown are also featured. FIGS.11 y and 11 z depict stiffening arrangements of novel and knownconnectors, respectively.

FIG. 12 depicts schematically a segment of a novel connector thatcombines the dog-clutch and the fitted (shear) pin principles. The hightorque capacity region is located near the external (metal) nipple sealsand the torque bearing protrusions extend partly through the wallthickness of the box.

FIG. 13 depicts schematically a segment of a novel connector thatcombines the dog-clutch and the fitted (shear) pin principles. The hightorque capacity region is located near the internal (metal) nipple sealsand the torque bearing protrusions extend partly through the wallthickness of the pin.

FIGS. 14 a through 14 e depict an example detail half view of arelatively low pressure (LP) to medium pressure (MP) connector providedwith novel structural modifications. Several examples of pin designdetails are featured.

FIGS. 15 a through 15 c depict example detail half views of LP to MPconnector box designs provided with novel structural modifications.

FIG. 16 depicts an example detail half view of a novel relatively highpressure (HP) connector design featuring axisymmetric threads.

FIG. 17 depicts an example detail half view of a novel HP connectordesign featuring axisymmetric threads and shear fitted pins arrangednear the outside nipple seals.

FIGS. 18 a through 18 c depict example design details of novelmechanical connectors.

FIG. 19 depicts schematically optional thread crest geometrymodifications.

FIG. 20 depicts a detail of a novel connector box interacting with a pinfeaturing a novel use of an assembly/disassembly fluid solidified incavities.

MODES OF CARRYING OUT THE INVENTION

The high structural torsional capacities of novel connectors areachieved by incorporating high capacity torque transfer components inthe design of the connectors, while the high torsional fatigue life isachieved by optimally shaping and accurately finishing the surfaces ofcomponents that transfer high torques between the objects connected. Theobjects connected can involve pipe or tube segments and/or elements ofoffshore or onshore structures. The said novel connectors incorporatealso structural elements typical to the design of the Merlin™ familyconnectors that provide them with high bending capacities, and whereverrequired also with high axial load capacities.

Several implementations of novel connectors are depicted on FIGS. 1through 20 .

Any connector according to this invention can be built out of metallicor non-metallic materials. That is reflected for sakes of examples onFIGS. 4, 6, 9, 10, 12, 13 and 20 by varying cross-section hatchings,with differing kinds of hatchings separated with pointed lines. On allother figures the uniform line hatchings used are understood torepresent either metallic or non-metallic materials.

FIGS. 1 and 2 show a novel connector featuring spline torque transferarrangement 160. FIG. 1 shows an exploded view of box 100 and pin 110,while FIG. 2 shows a cross-section through the same connector assembled.

It is noted that spline system (set) 160, 165 as shown in FIGS. 1 and 2can be also incorporated in FIG. 3 , FIG. 5 , it can be combined withany of FIGS. 7 through 10 or with FIGS. 11 a through 11 c, 11 e, 11 f,11 k, 11 s, 11 t, 11 w, 11 y , 12, 13, 14 a, 15 a through 17, 18 cand/or 20 similarly to the arrangement depicted for a sake of exampleson FIGS. 11 d, 11 g through 11 j, 11 l through 11 p, 11 r, 11 u, 11 vand/or 11 x, 11 y, 14 a through 14 e, 15 a through 15 c and/or 16through 20. All the above highlighted combinations of structural torquetransfer principles represent feasible designs of novel connectors.

In addition to spline torque transfer arrangement 160 this connectorimplements typical Merlin™ family features that are well known to thoseskilled in the art. The assembly and disassembly of all novel connectorsfeatured herein are similar and they are briefly outlined here byreference to FIGS. 1 and 2 .

Most novel connectors featured can be assembled either simply by(telescopic) pushing the box and the pin together, or they may need tobe assembled (telescopically) with the aid of fluid pressure contractingthe pin and expanding the box, which is the principle well known tothose skilled in the art. A disassembly is only feasible while usingfluid pressure, thus reversing the most common assembly operation thatalso utilizes an assembly fluid. That is carried out similarly to thecorresponding operational procedures relevant to the Merlin™ familyconnectors and some of their derivatives. The assembly/disassembly ofnovel connectors are reversible, i.e. they can be disassembled(telescopically) using fluid pressure and reassembled (telescopically)again. The (telescopic) assembly and/or the (telescopic) disassembly canbe carried out above or below the water surface.

During a telescopic assembly or disassembly with the aid of fluidpressure the annular compartment along an essentially frustoconicalinterface between a box and a pin is pressurized, so that a radialexpansion of the box and a radial contraction of the pin result in anenlargement of a radial gap between the box and the pin, so that threadtips of the interacting parts become clear of each other and the partscan be pushed together (or let to slide away from each other in acontrolled way) while a considerable force caused by the ‘end cap’pressure of the assembly/disassembly fluid attempts at all times to pushthe box and the pin away from each other. That happens without any, orsubstantially without excessive contact between the thread tips of thethreaded surfaces of the box and the pin. As soon as the connectormake-up overlap has been reached during an assembly, the fluid pressureis reduced the radial deformations of the pin and the box disappear, theexcess fluid is let out, all the threads snap into their final designpositions and the connector is made-up. The relative axial, telescopicmovement between the box and the pin is guided by essentiallycylindrical interaction surfaces of (metal) nipple seals that at alltimes seal the pressurized fluid compartment on its ends. A telescopicdisassembly is the reverse of the telescopic assembly.

Important design considerations pertaining to selecting heights ofprotrusions and depths of grooves used in the Merlin™ family connectorsat various axial locations of those connectors, as well, preferabletaper angles at various locations as well as means to improve thetelescopic assembly and/or disassembly operations with the use ofhydraulic pressure are disclosed for example in U.S. Pat. No. 8,056,940and those essentially apply to implementations of this inventiondescribed herein. Those design features, or their equivalents, can beoptionally applied to these designs, where applicable.

Identically to the known Merlin™ family connectors, each novel,mechanical connector, including a telescopically assembled mechanicalconnector, is provided with a zero pitch angle, axisymmetric threadlocated on substantially overlying, substantially matching,substantially frustoconical surfaces 2 extending essentially between twosets of (metal) nipple seals 140. One of said sets of (metal) nippleseals 140 is located near an end of box 100 and the other said set ofnipple seals 140 is located near an end of pin 110. It is known toanybody skilled in the art that each of said sets of (metal) nippleseals 140 incorporates telescopically engaging, substantiallycylindrical surfaces with an outside substantially cylindrical surfaceand an inside substantially cylindrical surface of a male substantiallycylindrical segment interacting radially through the mechanism of a hoopstress with substantially matching substantially cylindrical surfaces ofan annulus of a substantially cylindrical cavity 5. Said substantiallymatching substantially frustoconical surfaces 2 have in general variabletaper angles of lines 2 a, 2 b, 2 c, 2 d, 2 e, 2 f and 2 g shown for asake of examples on FIG. 2 . Lines 2 a, 2 b, 2 c, 2 d, 2 e, 2 f and 2 gextend along segments of said substantially matching, substantiallyoverlying substantially frustoconical surfaces 2, as shown. Anybodyknowledgeable in the art knows that taper angles of lines 2 a through 2g are measured between the tangents to said lines 2 a through 2 g andthe axis of the said connector. In particular line 2 d shown along asegment of splines 160 features for a sake of example a zero taperangle, a precise value is impossible to determine from FIG. 1 or 2 , andany variation within a small range or even within a greater range oftaper angles, like up to those pertaining for example to line 2 c oreven line 2 g do not affect the novelty of this invention. Anybodyknowledgeable in the art is aware that thread pitch angles are zero bydefinition for axisymmetric threads along for example lines 2 c or 2 e.The thread pitch angles are always independent on a small or largervalue of the local taper angle. Along spline segment 160 (line 2 d) thethread pitch angles are essentially equal to 90°, see FIG. 1 and thedescription of FIGS. 11 a through 11 x . Contact surfaces 145 adjacentto outside nipple seals are often referred to as outside abutmentsurfaces 145. Outside abutment surfaces 145 (or joint 145) provideeffective sealing between box 100 and pin 110, because at joint 145contact surfaces of box 100 and pin 110 are typically under axialcompression, as those knowledgeable in the field know. Essentiallyparallel surfaces 155 form a gap adjacent to inside nipple seals andthey are often referred to as inside abutment surfaces 155. Insideabutment surfaces 155 can provide additional sealing between box 100 andpin 110 if an O-ring or other elastic seal is inserted in their gap. Asthose knowledgeable in the field know, the gap of inside ‘abutment’surfaces 155 is necessary, because during the assembly or disassemblythe pin expands axially proportionally to its Poisson ratio as theresult of being compressed radially and simultaneously the box contractsaxially proportionally to its Poisson ratio, as it is being expandedradially. These combined actions result in decreasing of the width ofthe gap of inside ‘abutment’ surfaces 155 during assemblies anddisassemblies. Has there been no gap, it would not have been possible toassemble the connector, the threads would have never engaged in theirfinal assembly position. The opposite phenomena take place at outsideabutment surfaces 145, and that is why it is possible to design aconnector sealing at outside abutment surfaces 145. For connectorsutilizing dog clutch teeth to transfer torque (see further below),outside abutment surfaces 145 and/or inside abutment surfaces 155 can besplit into segments.

It is obvious from this description that thread pitch angle α at a givenpoint along a frustoconical surface is defined as:

$\alpha = {\lim\limits_{{\Delta\varphi}\rightarrow 0}\left\lbrack {a\tan\left( \frac{{2 \cdot \Delta}H}{{\Delta\varphi} \cdot D_{h}} \right)} \right\rbrack}$

where:

-   Δ_(φ)—infinitesimally small interval of the connector azimuth angle    measured in radians between the points at azimuth angle locations    −0.5·Δ_(φ) and +0.5·Δ_(φ) from the point along the thread line,    where angle α is being measured;-   ΔH—infinitesimally small axial distance along the connector span    over (corresponding to) the above −0.5·Δ_(φ) to +0.5·Δ_(φ) azimuth    angle interval measured in radians from the given point along the    thread line at which angle α is being measured;-   D_(H)—the pitch diameter of the thread at the point along the    thread, where angle α is being measured.    Whenever pitch H of a thread is constant along a frustoconical    surface of a connector (a most practical case and the most common    mathematical representation), the above formula simplifies and:

$\alpha = {{\lim\limits_{{\Delta\varphi}\rightarrow 0}\left\lbrack {a\tan\left( \frac{{2 \cdot \Delta}H}{{\Delta\varphi} \cdot D_{h}} \right)} \right\rbrack} = {a\tan\left( \frac{H}{\pi \cdot D_{H}} \right)}}$

For zero thread pitch angle α, axisymmetric threads pitch H=0, thereforeangle α is also zero. For left handed or right handed threads on afrustoconical surface H>0 and α>0, by definition. Whenever pitch H isconstant along a frustoconical surface, angle α varies slightly, becauseD_(H) varies along the connector. Wherever angle α is required to beconstant along a thread line, pitch H has to vary accordingly by keepingthe ratio of H to D_(H) constant, see the relations above. For splinestreated as special cases of threads, H is infinite and α=90°,because)tan (90°) is infinite, see FIG. 1 .

(Metal to metal) nipple seals 140 are used to seal a cavity between box100 and pin 110 that is filled with an assembly/disassembly fluid at thestage when the connector is only initially assembled. Nipple seals 140seal the said cavity, while the fluid is delivered through port 170.Fluid (hydraulic) pressure expands box 100 and ‘contracts’ pin 110 inthe radial direction through the mechanism of hoop straining andmeridional bending. The relation between the hoop stress(ing) σ and thehoop strain(ing) ∈ is known to anybody skilled in the art, because it isexpressed by the Hooke's Law: σ=∈·E, where E is the Young modulus. Thatenables the final assembly stroke in the axial direction that makes upthe connection by engaging zero-pitch angle threads 150, 155 of box 100and pin 110. Axisymmetric, zero-pitch angle grooves (threads) 150, 155can engage only in the correct axial position due to the use ofnon-uniform axial spacings of thread 155. Axisymmetric, zero-pitch anglethread 150, 155 is responsible for the transfer of axial and bendingloads as well as for the axial and radial pre-stressing of theconnector. Excess fluid is removed through fluid outlet ports 130 neareach end of the connector.

Novel connectors of high torsional and bending load capacity optionally,but quite often require precisely accurate azimuth angle orientations ofbox 100 relative pin 110. The azimuth orientation angles of box 100relative pin 110 are modified by rotating pin 110 relative box 100around the axis of the connector. In a case the azimuth assembly angleis specified, spline set (system) 160 (and optionally 165) canoptionally engage only in the correct circumferential position due tothe optional use of optional non-uniform angular spacings of trough 165(and of the matching optional spline tooth, not visible) in thecircumferential direction, so that the novel connector can optionally beassembled in only the prescribed design azimuth orientation. That ismost often the case.

In the connector shown in FIGS. 1 and 2 spline system (set) 160(optionally including spline 165) is arranged on cylindrical segments ofbox 100 and pin 110, which is optional and preferable, but splines canalso be shaped along tapered surfaces, essentially matching the averagelocal taper angles of the contact surfaces of box 100 and pin 110.

Similarly to splines used in machine engineering, splines 160 (andoptional splines 165) can be parallel-sided, they can have involuteshaped sides, they can have triangularly shaped spline teeth, they canhave straight teeth interacting with involute shaped teeth, etc., asrequired. If necessary radial and circumferential pre-loads can be usedby utilizing a required degree of interference fitting between splineteeth 160 (and optionally spline 165) of box 100 and pin 110. The latteris often the case depending on the design requirements, as it typicallyis in Merlin™ family connectors with regard to the axial and radialpre-loading. Spline teeth 160 (and optionally teeth 165) of theconnector shown in FIGS. 1 and 2 are examples, any known splinegeometries can be used.

Design features typically used for assembling/disassembling theconnectors shown in FIGS. 1 through 20 are deliberately omitted from thedrawings for simplicity. Annotations 15, 16 and 17 on FIG. 1 indicateoptions to use lining 15, cladding 16 and/or welding overlay 17 on anysurface of the connector, as required by design conditions. Lining 15,cladding 16 and/or welding overlay 17 most often with CorrosionResistant Alloys (CRAs) are shown on FIG. 1 for sake of example in ageneric way, because those can be used on any surface of any novelconnector shown on FIGS. 1 through 20 , according to particular projectrequirements, as it is known with regard to prior art connectors.

FIG. 3 presents a half view of a novel connector featuring key 305torque transfer arrangement. For simplicity only box 300 and pin 310 areannotated, the remaining design features shown are analogous to thosealready explained.

FIG. 4 shows a detail of key 305 interacting with box 300 of theconnector in FIG. 3 . Key 305 shown in FIGS. 3 and 4 is sunk in pin 310.Gap 307 is shown between outside face 302 of key 305 and the depth ofthe key groove provided in box 300. Axisymmetric, zero-pitch anglethread is designated with 350 and 355; 355 is pertaining to non-uniformaxial spacing grooving designed to prevent accidental incorrectassembly. The longitudinal axis of key 305 shown is parallel to theaverage taper of the interacting surfaces of box 300 and pin 310 alongthe length of the key, which is preferred, but that does not need be thecase in other designs.

The precise shape of the example outside face 302 of key 305 isimpossible to see in the figures. In order to allow for some bendingrigidity of key 305 during the final stage of the assembly, while box300 and pin 310 flex in meridional bending because of a pressurization,groove 315 can be optionally provided. Groove 315 may not be required incases when outside face 302 of key 305 is rounded to match the outsidemajor diameters of the axisymmetric grooving of pin 310 (not shown inFIG. 4 and not annotated on FIG. 3 ). Rounding outside face 302 of key305 is preferable, either to match the outside contour of majordiameters of the axisymmetric pin grooving, or equal to the minimumvalue of the major diameter of the axisymmetric pin grooving along thelength of key 305, so that the outside corners of key 305 (sides ofoutside face 302) never protrude outside of the contour of the adjacentgrooving of pin 310. Key 305 is best interference fitted into itschannel in pin 310, and preferably also (preferably loosely) bolted topin 310 (optional screw not shown) or otherwise secured, in order toavoid a possibility of jamming during a disassembly or assembly of theconnector. The sides of key 305 are preferably also interference fittedinto the key channel in box 300.

In FIGS. 3 and 4 key 305 shown is double-rounded, but that is for thesake of an example only. Practically all types of key connections usedin machine engineering can be used with novel connectors. Those includefeather keys, square keys, flat keys, beveled keys, Woodruff keys, taperkeys, etc.

The key inserts can be alternatively provided with circular, oval,elliptical, or other curvilinear cross-sections. It is noted, however,that more machine-connection-like key cross section shapes, like squareor rectangular cross sections with only slightly rounded edges havehigher bearing load capacities than have those provided by keys havingcircular or elliptical cross sections.

Depending on the torque capacity of the connector required for aparticular design, multiple keys can be arranged around thecircumference of the connector (multiple o'clock positions), which ispreferably the case. Those keys can be arranged in one circumferentialrow, like in case of FIG. 3, 11 f, 11 l, 11 r, 11 w, 11 x or/and 11 y,with additional keys not visible, or in several rows (see schematicillustrations in FIG. 11 e ), in staggered rows or in irregulararrangements (see schematic illustration in FIG. 11 f ). It is notedthat key system 305 as shown on FIG. 4 can be also incorporated in thedesign shown on FIG. 5 , it can be combined with any of FIGS. 7 through10 or with any of FIGS. 11 a through 11 d, 11 g through 11 k, 11 mthrough 11 q, 11 s through 11 v, 11 x, 11 y , 12, 13, 14 a through 14 e,15 a through 15 c and/or 16 through 20. All the above highlightedcombinations represent feasible designs of novel connectors.

In a case of an ‘off a shelf’, or retrofitted Merlin™ family connectorbeing adapted to carry high torsional loads, it may be acceptable tosacrifice some of the original axial and even bending capacity of theconnector in order to upgrade its torsional load capacity by addingsystems (sets) of keys 305.

If required, keys 305 are optionally, but typically, arranged around thecircumference in a non-uniform circumferential pitch or/and pattern, inorder to assure the connector assembly with the prescribed azimuthorientation of box 300 relative pin 310.

FIG. 5 presents a half view of a novel connector featuring shear(fitted) pin 505 torque transfer arrangements. Multiple fitted pins sets505 can be arranged around the circumference of the connector in theregion of one of the connector ends or simultaneously in regions of bothends as it is shown on FIG. 5 . The use of shear pins 505 simultaneouslyat both connector ends is preferable, because that limits frictionalload differential between the interaction surfaces of box 500 and pin510. Shear pins 505 can be arranged in a single row at each end, or inmultiple rows (sets) that may or may not be staggered with regard toeach other in the radial and/or circumferential direction(s), see forexample FIG. 17 . Only one row of shear pins 505 is shown near each endin FIG. 5 , for the sake of an example. If required, shear pins 505 areoptionally, but typically, arranged with a non-uniform circumferentialpitch (spacing) or pattern in order to assure the connector assemblywith the correct azimuth orientation of box 500 relative pin 510.

FIG. 6 shows details of shear (fitted) pins 505, 605 interacting withpins 510, 610 and with boxes 500, 600 according to this invention, onefor each end of the interacting surfaces. The top detail depicted inFIG. 6 is that of the connector shown in FIG. 5 ; see the bottom rightcorner of FIG. 5 . The bottom detail in FIG. 6 is that of anothersimilar connector, note the differing dimensional proportions of box600, pin 610 and fitted pin 605. In particular note circumferentialgroove 615 in the box that is used in order to increase locally themeridional flexibility of box 600. Similar grooves or systems ofmultiple grooves increasing locally the structural flexibility can bearranged in corresponding locations or in other regions of boxes and/orpins, in particular in the regions adjacent to (metal) nipple seals.Depending on particular design requirements those may be beneficial inany connector depicted on FIGS. 1 through 20 or otherwise discussedherein.

Connectors featuring fitted pins 505, 605 can be economical in design,retrofitted with shear fitted pins or otherwise adapted for particulardesign requirements, because shear pins 505, 605 or alike can be easilylocated in regions of relatively low structural loading. Holes to fitshear pins 505, 605 are relatively easy to drill, shim or/and tap ifthreads are required to whatever geometries may be selected. Typicallyinterference fitting of shear pins 505, 605 or alike may be requireddepending on particular design needs.

Shear (fitted) pins 505, 605 can be optionally screwed into one of theparts being connected or/and bonded with an adhesive, see also FIGS. 12,13, 17 and 18 b. O-rings, metal ring seals or other sealing arrangementscan be used in order to protect shear pins 505, 605 from seawater andfrom internal fluids, as applicable. CRAs, titanium alloys, aluminumalloys, magnesium alloys, nickel based alloys, steels, other materials,cladding with CRAs, weld overlaying with CRAs or encapsulating ofinteracting regions in protective resins, etc. can be used with novelconnectors featured herein. It is noted that fitted pins 505, 605 asshown on FIG. 6 can be also incorporated in the designs shown on FIGS. 1through 3 , or they can be combined with any of FIGS. 7 through 10 orwith any of FIGS. 11 a through 11 l, 11 n, and 11 s through 11 v , FIG.11 x, 11 y, 14 a, 15 a through 15 c, 18 c , 19 and/or 20. All the abovehighlighted combinations represent feasible designs of novel connectors.

FIG. 7 depicts a detail of a novel connector assembled. The dog-clutchtorque transfer principle is utilized near the outside surfaces of pin710 and box 700. Dog-clutch teeth 780, 706, 716 utilize the fullmaterial thickness available between the (metal) nipple seal region andthe outside surface of the connector, which is not fully visible on thefigure.

If required, dog-clutch teeth 780, as well as optional dog-clutch teeth706 and 716, are typically arranged around the circumference in anon-uniform circumferential pitch or/and pattern, in order to assure theconnector assembly with the correct azimuth orientation of box 700relative pin 710. Optional teeth 706/716 have for that purposeoptionally different circumferential dimensions than teeth 780 have.

FIG. 8 depicts in an exploded view a detail of a novel connector. Thedog-clutch torque transfer principle is utilized near the outsidesurfaces of pin 810 and box 800. Dog-clutch teeth 880, as well asoptionally differently dimensioned dog-clutch teeth 806 and 816 utilizea partial material thickness available between the (metal) nipple sealregion and the outside surface of the connector.

It is known to anybody skilled in the art that long life torsionalfatigue strength of circular cross-section components (like for exampleturbine shafts) is less sensitive to the working cross-section changesthan bending fatigue is. However, for this application high torsionalfatigue strength is important and the preferred designs utilizerelatively large fillet radii 702, 802 and 712, 812 for the concaveregions of component edges. In particular large fillet radii 702, 802are used on FIGS. 7 and 8 for box 700, 800 concave edge regions andlarge fillet radii 712, 812 are used for pin 710, 810 concave edgeregions. For convex edge regions the shapes are not critical for fatiguelife and chamfers 704, 804 are shown for the convex edge regions ofboxes and 714, 814 for the convex edge regions of pins, but fillets canbe also used instead. High torsional load capacity arrangements 780,880, as well as optional dog-clutch teeth 706 and 806, 716 and 816 showncan feature optionally non-uniform circumferential pitch of shapes 706,806 and 716, 816 on boxes 700, 800 and pins 710, 810 respectively, inorder to assure that the connector can be optionally assembled only inits prescribed azimuth orientation of pins 710, 810 relative boxes 700,800, respectively.

FIG. 9 depicts a detail of a novel connector assembled. The dog-clutchtorque transfer principle is utilized near the inside surfaces of pin910 and box 900. Dog-clutch teeth 990, as well as optionally differentlydimensioned dog-clutch teeth 996, utilize the full material thicknessavailable between the (metal) nipple seal region and the inside surfaceof the connector, which is not fully visible on the figure.

If required, dog-clutch teeth 990, as well as optional dog-clutch teeth996, can be optionally, but typically, arranged around the circumferencein an optional non-uniform circumferential pitch or/and pattern, inorder to assure the connector assembly with the prescribed azimuthorientation of box 900 relative pin 910. Optional teeth 996 can have forthat purpose different circumferential spacing than teeth 990 have.

FIG. 10 depicts in an exploded view a detail of a novel connector. Thedog-clutch torque transfer principle is utilized near the insidesurfaces of pin 1010 and box 1000. Dog-clutch teeth 1080, as well asoptional dog-clutch teeth 1006 and 1016, utilize a partial materialthickness available between the (metal) nipple seal region and theinside surface of the connector.

If required, dog-clutch teeth 1080, as well as optional dog-clutch teeth1006 and 1016, can be optionally, but typically, arranged around thecircumference in an optional non-uniform circumferential spacing or/andpattern, in order to optionally assure the connector assembly with theprescribed azimuth orientation of box 1000 relative pin 1010. Optionalteeth 1006/1016 have for that purpose different circumferential spacingthan teeth 1080 have.

For applications where high torsional fatigue strength is important andthe preferred designs utilize relatively large fillet radii 1002 and1012 for concave regions of component edges. In particular large filletradii 1002 are used for box 1000 concave edge regions and large filletradii 1012 are used for pin 1010 concave edge regions. For convex edgeregions the shapes are not critical for torsional strength and chamfers1004 are shown for the convex edge regions of box 1000 and 1014 for theconvex regions of edges of pin 1010, but fillets can be also usedinstead.

The design of the protruding teeth and matching hollows carryingtorsional loads can be reversed between the boxes and the pins withoutaffecting the functionality of this invention in the examples shown onFIGS. 7 through 10 . A mixed reversed/not reversed design can also beused instead of that shown.

Connectors featuring the dog-clutch torque transfer arrangements can beeconomical in design for particular requirements, because torquetransfer teeth 780, 706, 716, 880, 806, 816, 990, 996, 1006, 1016 can beeasily located in regions of relatively low structural loading as shownin FIGS. 7 through 10, 12 and/or 13 . Dog-clutch teeth arrangements likethose shown in details on FIGS. 7 through 10 can be also incorporatedfor example in any of the designs shown on FIGS. 11 a through 11 m, 11o, 11 q, 11 s, 11 u, 11 v, and/or 14 a through 20. All the abovehighlighted combinations represent feasible designs of novel connectors.

Whenever the torque transfer arrangements are located simultaneously onboth ends [near both (metal) nipple seal systems in the same connector,novel connectors utilizing fitted pins 505, 605 or dog-clutch torquetransferring teeth 780, 706, 716, 880, 806, 816, 990, 996, 1006, 1016characterize with most of the torque being transferred through theconnector structures, while largely by-passing those main contactsurfaces between the boxes and the pins that transfer the axial andbending loads.

FIGS. 11 a through 11 y depict for the sake of example designimplementations of torque transfer mechanisms featured used separatelyand in combinations. Variations in structural segment sequencing alongthe example connectors shown are also featured.

Example design implementations of novel mechanical connectors shown inFIGS. 11 a through 11 y provide differing load transfer functionsbetween box 1100 and pin 1110 are separated longitudinally into segments(sets). Surfaces 1111 of frustoconical pitch diameters (averageddiameter) are depicted schematically with dashed lines. Those extendbetween (metal) nipple seals near each of the connectors, which areshown on FIGS. 11 a through 11 y with short lines parallel to theconnector axes, but not annotated. Groove/protrusions systems (alsoreferred to herein as grooving) along frustoconical surfaces 1111 areshown schematically with groups of thin continuous lines. In general,the taper angles of the frustoconical surfaces of box 1100 and pin 1110vary along the lengths of the connectors. The same is in general thecase with other connectors like those shown on FIGS. 1 through 20 .Fitted (shear) pin systems (sets) are indicated with rows of hollowshapes with barbs. Dog-clutch tooth systems are shown with rectangularzig-zag lines.

Because generic families of connectors are represented onlyschematically on FIGS. 11 a through 11 y , the same generic annotationsare used for simplicity on FIGS. 11 a through 11 y for all the genericcomponents corresponding in connectors of differing designs:

-   -   Known types of grooving (thread) providing static and fatigue        transfer of axial and bending loads are annotated 1140        (axisymmetric, zero pitch angle, i.e. α=0°);    -   Thread grooving featuring absolute values of pitch angles (fixed        or variable) greater than 0° and smaller than 90° (0°<α<90°)        according to this invention are annotated 1120 and 1121 for        general left-handed and general right-handed threads        respectively; additionally left handed threads and right handed        threads that have pitches significantly differing (i.e. greater        or smaller) from those annotated 1120 and/or 1121 used in the        same connector are annotated 1125 and 1126, respectively.        Groovings 1120, 1121, 1125 and 1126 combine the functions of        transfer of axial, bending and torsional static and dynamic        (fatigue) loads; pitch angles of left-handed or right-handed        threads generally vary slightly along a frustoconical segment of        the connector, while always satisfying 0°<α<90°, but for        telescopically assembled connectors discussed herein they can        undergo arbitrary variations along connectors or be in        particular constant along a connector, if desired so (thus        describing a conical helix, or concho-spiral), even though in        general there may be no reason for keeping angle α constant;    -   Spline (grooving) sets according to this invention that        transfers torsional static and dynamic loads are annotated 1130        (absolute value pitch angles essentially equal to 90°, α=90°,        because splines can be regarded as threads having infinite axial        pitch; note that the tangent of 90° is infinite);    -   Systems (sets) of keys used for torque transfer are annotated        1107 for keys arranged in circumferential rows and 1117 for        axially staggered key patterns, or for keys distributed        irregularly on surfaces 1111;    -   Systems (sets) of fitted shear pins used for torque transfer are        annotated 1150;    -   Systems (sets) of dog-clutch teeth used to transfer torque and        situated in the outside or in the inside abutment areas are        annotated 1160.

The numbers and/or sequences of segment (set) types shown in anyschematic view included on FIGS. 11 a through 11 z and their relativeaxial arrangements are incidental and these values/features can bemodified arbitrarily without changing the type of implementation of thisinvention.

FIG. 11 a depicts an example implementation of a novel connectorfeaturing two segments with grooving (thread) type 1140 and one segmentwith left-handed grooving (thread) type 1120. The example shown in FIG.11 a equally represents its mirror image with a replacement of grooving(thread) type 1120 with right-handed grooving (thread) type 1121, asshown on FIG. 11 k.

FIG. 11 b depicts an example novel connector featuring two segments withgrooving type 1140 and two non-zero pitch angle segments with threadtypes 1120 and 1121. Segment 1120 utilizes a left-handed thread andsegment 1121 utilizes a right-handed thread.

FIG. 11 c depicts an example novel connector featuring several segmentswith grooving (thread) type 1140, a segment with thread type 1120 and asegment with thread type 1121. Segment 1120 utilizes a left-handedthread and segment 1121 utilizes a right-handed thread.

FIG. 11 d depicts an example novel connector featuring two segments withgrooving (thread) type 1140, one segment (set) with spline grooving type1130, a segment with thread type 1120 and a segment with thread type1121 (see also FIGS. 1 and 2 ). It is understood that similar systemsutilizing multiple spline sets (segments) 1130 can also be used inconnectors featuring also segments type 1120 and/or 1121, in connectorsutilizing only segments type 1140 and sets type 1130, see FIGS. 1, 2, 11g through 11 j, 11 l through 11 p, 11 r, 11 x or/and 11 y for examples.

FIGS. 11 e and 11 f depict example novel connectors featuring known typeof axisymmetric, zero-pitch angle grooving 1140 that is utilized totransfer axial and bending loads between box 1100 and pin 1110 with keyinserts 1107, 1117 essentially following local taper angles of the pitchdiameter surfaces 1111 of box 1100 and pin 1110. Any geometrical shapesand types of key inserts 1107, 1117 can be used. It is noted however,that the key-grooves and the key-inserts need not necessarily follow thelocal taper angles in many similar connectors. They may or may not bearranged essentially in straight lines and in addition to being arrangedessentially in axial (meridional) planes, they can also be arranged atnon-zero angles to the said axial (meridional) planes of the said novelconnector.

Although that does not necessarily need to be the case, it is preferredthat key inserts have as slim design as possible, in particular in theradial direction of the connector. If feasible, the grooving used toinsert the keys utilized in this invention should preferably notpenetrate inside the material of box 1100 or pin 1110 deeper thangrooving type 1140, or/and types 1120 or/and 1121 if also used in thesame connector (see also FIGS. 3 and 4 ).

However, in particular where the length of the said connector is theissue, or when the axially symmetric grooving is very shallow, deepergrooving than that outlined above may need to be used with key grooving1107, 1117 utilized in the said novel connectors. Shallow grooving 1107,1117 may weaken bending load capacities of connectors only minimally.

Non-zero pitch angle thread segments 1120, 1121, while used separatelywould only allow a reliable torque transfer in one rotational direction,that which tightens the tapered thread. Applying a torque in theopposite direction would have unscrewed the connection. Both these factsare well known to those skilled in the art, because they are widely usedin threaded connections, including for example tapered threadeddrill-pipe connectors. However, in novel connectors the unscrewing ofeither thread 1120 or 1121 is prevented because of the interlocking withother types of grooving 1140, 1121, 1120, or/and 1126, 1125 respectivelyand novel connectors like for example those shown on FIGS. 11 a through11 d, 11 k, 11 o through 11 v, 11 x and/or 11 y are very effective inthe transfer of torsional loads in both opposite rotational directions.In novel connectors featuring only segments with thread direction 1120(see FIG. 11 a ) or 1121 (see FIG. 11 k or/and 11 q) the unscrewing isprevented by interlocking (via an axial load) with axisymmetric grooving1140. On connectors that utilize non-zero pitch angle thread 1120 and1121 (FIGS. 11 b, 11 c and 11 d ) thread 1120 is torsionally interlockedagainst the opposite thread, with grooving 1140 and in the case of thesystem shown in FIG. 11 d spline set (system) 1130 helping additionally.Interlocking in the torsional load direction is also effectedsimultaneously with any other structural arrangements used optionally,or in order to increase the torque transfer capacities of novelconnectors, see multiple examples shown and/or described herein.

FIG. 11 g features spline (rows) sets 1130 arranged outsideaxisymmetric, zero pitch angle grooving 1140 arranged along interface1111 of box 1100 and pin 1110.

FIGS. 11 h through 11 j feature each several spline (rows) sets 1130arranged interchangeably between axisymmetric, zero pitch angle thread1140 arranged along interface 1111 of box 1100 and pin 1110.

FIG. 11 k depicts an example novel connector featuring two segments withgrooving (thread) type 1140 and one segment with grooving (thread) type1121. The example shown in FIG. 11 k equally represents its mirror imagewith a replacement of grooving (thread) type 1121 with grooving (thread)type 1120, as shown on FIG. 11 a.

FIG. 11 l depicts an example novel connector featuring three segmentswith grooving (thread) type 1140, two segments (sets) of splines 1130arranged between the segments of axisymmetric threads 1140 and keysystem 1107.

FIG. 11 m depicts an example novel connector featuring four segmentswith grooving (thread) type 1140, three segments (sets) of splines 1130arranged between the segments of axisymmetric threads 1140 and twosystems of fitted shear pins at each connector end.

FIG. 11 n depicts an example novel connector featuring four segmentswith grooving (thread) type 1140, three segments (sets) of splines 1130arranged between the segments of axisymmetric threads 1140 and systemsof dog-clutch teeth 1160 at each connector end.

FIG. 11 o depicts an example novel connector featuring four segmentswith grooving (thread) type 1140, three segments (sets) of splines 1130,single segments of non-zero pitch angle threads 1120 and 1121 each, andsystems of fitted shear pins 1150 at each connector end.

FIG. 11 p depicts an example novel connector featuring four segmentswith grooving (thread) type 1140, three segments (sets) of splines 1130,single segments of non-zero pitch angle threads 1120 and 1121, a system(set) of fitted shear pins 1150 near the outside (metal) nipple sealsand a system (set) of dog-clutch teeth 1160 near the inside (metal)nipple seals.

FIG. 11 q depicts an example novel connector featuring two segments withgrooving (thread) type 1140, one segment with right-handed thread 1121and systems (sets) of fitted shear pins 1150 at each connector end.Example novel connector shown in FIG. 11 r implements a combination of 5structural torque transfer arrangements featured herein implemented in asingle design.

FIG. 11 r depicts an example novel connector featuring three segmentswith grooving (thread) type 1140, two segments (sets) of splines 1130,single segments of non-zero pitch angle threads 1120 and 1121 each, asystem (set) of keys 1107, a system of fitted shear pins 1150 near theoutside (metal) nipple seals and a system of dog-clutch teeth 1160 nearthe inside (metal) nipple seals. Example novel connector shown in FIG.11 r implements a combination of 6 structural torque transferarrangements featured herein implemented in a single design.

FIG. 11 s depicts an example novel connector featuring two segments eachof non-zero pitch angle threads 1120 and 1121, four segments in total.

FIG. 11 t depicts an example novel connector featuring single segmentseach of non-zero pitch angle threads 1120 and 1121 and a system (set) ofdog-clutch-teeth 1160 arranged near the inside (metal) nipple seals.

Note that FIGS. 11 s through 11 v do not feature axisymmetric thread1140, which is acceptable, because each of threads 1120, 1121, 1125 and1126 also transfer axial and bending loads. In fact threads 1120, 1121,1125 and/or 1126 can be used in novel connectors without a use of zeropitch angle segment(s), providing that they are interlocked with atleast one of the other structural torque transfer sets: splines, keys,fitted pins, dog-clutch pins or even other segment(s) of thread 1125,1126, 1120 and/or 1121 respectively (i.e. those in the same directions,i.e. same-handed, see FIGS. 11 u and 11 v ), providing that they usesufficiently differing pitch angle values, so that torsionalinterlocking would occur. It is, however, preferred to use pairs ofopposite-handed thread segments with thread interlocking in mind;opposite-handed pairs meant as pairing left-handed thread segments withright-handed segments and vice versa.

FIG. 11 u depicts an example novel connector featuring a segment ofright-handed thread 1121 and a same-handed, i.e. also right-handedsegment of thread 1126 having a pitch angle differing from that ofthread segment 1121.

FIG. 11 v depicts an example novel connector featuring a segment ofleft-handed thread 1120 and a same-handed, i.e. also left-handed segmentof thread 1125 having a pitch angle differing from that of threadsegment 1120.

FIG. 11 w depicts an example novel connector featuring three segmentswith grooving (thread) type 1140, a segment (set) of keys 1107, twosystems (sets) of dog-clutch teeth 1160 at each connector end twosystems (sets) of fitted shear pins 1150 at each connector end.

FIG. 11 x depicts an example novel connector featuring three segmentswith grooving (thread) type 1140, two segments (sets) of splines 1130,single segments of non-zero pitch angle threads 1120 and 1121 each, asystem (set) of keys 1107 and systems (sets) of dog-clutch teeth 1160near each end of the connector. Example novel connector shown in FIG. 11x implements a combination of 5 structural torque transfer arrangementsfeatured herein implemented in a single design, with a system of fitted(shear) pins not used.

FIG. 11 y depicts an example novel connector featuring three segmentswith grooving (thread) type 1140, two segments (sets) of splines 1130,single segments of non-zero pitch angle threads 1120 and 1121 each, asystem (set) of keys 1107, two systems (sets) of (fitted) shear pins1150 and systems (sets) of dog-clutch teeth 1160 near each end of theconnector. All but one sets of structural arrangements designed totransfer torque are optional. FIG. 11 y also depicts schematicallyoptional external 1170 and internal 1180 sets of stiffening arrangementsaccording to this invention that can essentially be for example annularstiffening clamps.

FIG. 11 z depicts an example known connector featuring five segmentswith axisymmetric grooving (thread) type 1140. FIG. 11 z also depictsschematically optional external 1170 and internal 1180 sets ofstiffening arrangements according to this invention that can essentiallybe for example annular stiffening clamps.

External clamp 1170 and/or internal clamp 1180 depicted on FIG. 11 y andon FIG. 11 z have as their purpose structural restricting essentially ofthe box shell from radial deformations outwards (outbound, i.e. awayfrom the connector axis) and structural restricting essentially of thepin shell from radial deformations inwards (inbound, i.e. towards theconnector axis), respectively. Clamp 1170 and clamp 1180 keep thethreads between the boxes and shells firmly engaged both locally andglobally. External clamp 1170 essentially restricts the box shell fromradial deformations outwards, however it is a good practice to extend itbeyond the abutment joint of outside nipple seals, accordingly it alsorestricts a part of the outside pin surface from radial deformationsoutwards. Internal clamp 1180 essentially restricts the pin shell fromradial deformations inwards, however it is a good practice to extend itbeyond the ‘abutment’ surfaces of inside nipple seals, accordingly italso restricts a part of the inside box surface from radial deformationsinwards. The inside ‘abutment’ is by necessity a gap that can be sealedwith an O-ring, or similar. Accordingly, because of the radialrestricting actions of external clamp 1170 and/or internal clamp 1180depicted on FIG. 11 y and on FIG. 11 z , the connector threads engagedon the frustoconical surfaces of the box and the pin are essentiallyengaged in an essentially compressive ‘vise grip’ acting through amechanism of radial interference fit in the radial direction at allo'clock locations around the circumference of the box and the pin of theconnector. The term ‘essentially compressive vise grip’ isself-descriptive with regard to compressing radially the female and maleinteracting thread surfaces together. It is defined as essentiallycompressing radially together the female thread surface and the malethread surface interacting with said female thread surface, as if theywere engaged in a compressive grip of an imaginary vise. The strength ofthe said vise grip varies from very light, to very strong, depending onparticular design needs.

Clamps 1170 and/or 1180 that extend beyond the abutment surfaces ofnipple seals additionally help to seal the nipple seal surfaces and theymay also provide their own sealing surfaces on the areas of interactionswith the boxes and/or with the pins. O-rings, or other seals or gasketscan be optionally added between the clamps and/or the box and/or the pinon both sides of the outside and inside abutment areas. In cases whereclamps 1170 and/or 1180 are segmented gaskets or other seals can beadded to seal areas of segment interactions. For connectors utilized inlow pressure installations silicone sealant or similar can be used. Thepurpose of clamps 1170 and/or 1180 is also the stabilization ofessentially circular cross-sections structurally by essentiallystrengthening the boxes and/or the pins, respectively. That involvestheir design shape stabilizations by stiffening the connectors under anycombinations of axial, bending and torsional loads. Clamps 1170 and/or1180 are installed after the connectors are assembled, and they aretypically removed before their disassemblies. While in place, clamps1170 and/or 1180 restrict radial expansion of boxes and/or radialcompression of pins and thus prevent disengaging of threads connectingboxes and pins. External clamp 1170 and/or internal clamp 1180 depictedon FIG. 11 y and on FIG. 11 z essentially conform to the externalsurfaces of the boxes and to the internal surfaces of the pins,respectively. Optionally but preferably, external clamps 1170 depictedon FIG. 11 y and on FIG. 11 z are installed with interference fits, sothat the internal surfaces of external clamps 1170 are in interferencefits with the conforming external surfaces of their boxes. Similarly,optionally but preferably, internal clamps 1180 depicted on FIG. 11 yand on FIG. 11 z are installed with interference fits, so that theexternal surfaces of internal clamps 1180 are in interference fits withthe conforming internal surfaces of their pins.

External clamps 1170 and/or internal clamps 1180 depicted on FIG. 11 yand on FIG. 11 z are clamped to corresponding boxes and/or pinsrespectively. External clamp 1170 and/or internal clamp 1180 interactstructurally with their adjacent boxes and/or pins while remainingessentially unbonded to their adjacent boxes and/or pins, but they mayutilize matching (conforming) locating grooves and/or recesses. Thematching (conforming) locating grooves and/or recesses may be arrangedcircumferentially, longitudinally or at acute angles to the connectoraxes. Known or novel connectors depicted on FIG. 11 y and on FIG. 11 zmay also utilize repositionable/removable ‘sticky adhesive’ areas,cotter pins, safety wire, etc. that are essentially non-structural andthey are used substantially to keep external clamps 1170 and/or internalclamps 1180 depicted on FIG. 11 y and on FIG. 11 z in their designlocations relative the boxes and/or pins they interact with.

External clamps 1170 and/or internal clamps 1180 according to thisinvention depicted on FIG. 11 y and on FIG. 11 z can be split along oneor more o'clock locations on their circumferences in order to assure aneasy assembly, typically at some stage after the pins and the boxes areassembled telescopically, or they can form continuous sleeves. Splittingsurfaces can be arranged in planes with connector axes, they can beslanted at acute angles to the connector circumferential surfaces.Splitting surfaces can also run at acute angles to connector axes,follow essentially helicoidal guiding lines, etc. Additional reasons forat least one of external clamps 1170 and/or internal clamps 1180 to beinstalled after the telescopic assembly of the connector is completedinclude the fact that known Merlin™ family connectors are typicallydesigned in a critical way and a presence of fixed (bonded) external orinternal stiffenings of boxes and pins would have made the telescopicassembly or disassembly of the connector impossible. In particular witha use of boxes and/or pins and/or clamps 1170 and/or 1180 made ofelastomeric materials and/or essentially hyperelastic materials (likerubber, isoprene, neoprene, some other natural or synthetic materialsthat model essentially well as hyperelastic materials, etc.), it may befeasible to slide on outside or in inside the connectors continuoussleeve clamps that are not split along their circumferences or clampsthat are split along single o'clock locations. Ramrods and/or pigsand/or robots can be used for help in installations of internal clamps1180 with the clamp pre-positioned before installation near theconnector, or pushed in along a greater length of a pipe beingconnected. Ramrods and/or pigs and/or robots can include positioning,fitting and/or other tools, or/and they can be provided with tool-heads,etc., which may be optional or necessary depending on particulardesigns. External sleeve clamps, or external clamps split along singleo'clock locations can also be prepositioned near the connector beforetheir telescopic assemblies.

Sets of stiffening, clamping arrangements 1180 can have their insidediameters faired with the internal diameters of known or novelconnectors, so that they are essentially the same as those of theconnectors, as shown schematically on FIGS. 11 y and 11 z . Elastomericmaterials perform essentially in a hyperelastic ways, but many othernatural or synthetic materials can be also modeled as essentiallyhyperelastic materials. The elongation in such materials can berelatively high; an order of magnitude of up to around 400% is quitecommon; this is very high in comparison with high strength metallicmaterials, which reach plastic strains (elongations) of the order of0.3% to 0.53%, (or even up to 0.67% for some titanium alloys) when oneis considering metals that can be used for manufacturing known Merlin™family connectors. What follows are correspondingly greater thread teethheights versus material thickness in connectors utilizing non-metallicmaterials, like elastomeric materials in comparison with high strengthmetals. Utilizing external clamps 1170 and/or internal clamps 1180according to this invention depicted on FIG. 11 y and on FIG. 11 z inthe design of Merlin™ family connectors built from non-metallicmaterials, like elastomeric or other natural or synthetic is typicallyvery important. In addition to the roles of external clamps 1170 and/orinternal clamps 1180 already described, the clamps are typicallydesigned to additionally seal the connectors and decrease theprobability of eventually developing leaks. External clamps 1170 and/orinternal clamps 1180 according to this invention depicted on FIG. 11 yand on FIG. 11 z stiffen the boxes and/or pins they clamp regardingdeflections caused by any combinations of axial, bending and torsionalloads. They are also designed to prevent accidental penetration ofinternal or external fluids into the annuli between the boxes and thepins and thus they are designed to prevent accidental disassemblies ofconnectors because of fluid pressure penetrations into the annuli and/orother similar leaks. Because of the essential interference fits theyimprove the engagements of axisymmetric and/or left handed and/or righthanded threads and prevent global or local disengagements of the saidthreads that might happen under excessive axial and/or bending and/ortorsional loads of the connectors, as applicable. External clamps 1170and/or internal clamps 1180 according to this invention depicted on FIG.11 y and on FIG. 11 z are also very effective in preventing buckling,including cardioidal buckling of components of connectors featuringslender design and/or that of connectors made of synthetic or naturalnon-metallic materials that are more elastic than metallic materialstypically are. Other types of shapes becoming unstable (buckling)relevant here may involve local flattening of cross-sections or ‘kinks’(typically occurring under local bending and or bending combined withtorsion and/or with axial loads; those ‘kinks’ are not dissimilar togarden hose kinks). Stiffener web buckling and/or asteroidal buckling ofcomponents under excessive torsional loads, or torsional loads coupledwith bending and/or axial loads may also occur. The above loss ofstability (or buckling) modes may be particularly relevant to connectorsof light and/or slender design and to connectors utilizing in theirconstruction composite materials, elastomeric materials and/oressentially hyperelastic materials (like rubber, isoprene, neoprene,some other natural or synthetic materials that model essentially well ashyperelastic materials, etc.) and/or external clamps 1170 and/orinternal clamps 1180 according to this invention depicted on FIG. 11 yand on FIG. 11 z are particularly effective in preventing the sectionloss of stability (buckling).

Cardioidal buckling occurs in general under bending and/or axial loads,but torsion may also be involved. Typically an essentially circularcross-section collapses inwards along its o'clock location that resultsin assuming a roughly cardioidal (or U-shaped) form that propagatesalong the connector, pipe or tube. When some kind of laminated design isinvolved, like that of a box and pin assembled in a known or novelMerlin™ family connector, cardioidal buckling is more likely to affectinternal layer(s), i.e. pins herein, following by a very likelyunplanned, i.e. accidental disconnection. External clamps 1170 and/orinternal clamps 1180 according to this invention depicted on FIG. 11 yand on FIG. 11 z are introduced herein to prevent that and other formsof buckling like section flattening, asteroidal buckling, etc.Asteroidal buckling can occur under predominantly torsional loads. Whenthose loads become too high, material or shape non-uniformities maypromote bulging of some (several) o'clock location(s) of a cross-sectioninwards (towards the center of the cross-section), which can propagateaxially and circumferentially along essentially (several) helicoidalline(s).

In their construction external clamps 1170 and/or internal clamps 1180according to this invention depicted on FIG. 11 y and on FIG. 11 z canutilize:

-   -   friction welding,    -   injection molding,    -   3-Dimensional printing.        External clamps 1170 and/or internal clamps 1180 according to        this invention depicted on FIG. 11 y and on FIG. 11 z can        include stiffening ribs.

External clamps 1170 and/or internal clamps 1180 according to thisinvention depicted on FIG. 11 y and on FIG. 11 z can be made of at leastone of:

-   -   a high strength steel,    -   or a corrosion resistant alloy,    -   or a titanium alloy,    -   or an aluminum alloy,    -   or a magnesium alloy,    -   or a nickel based alloy,    -   or a non-metallic material including a plastic material,    -   or a non-metallic natural or a non-metallic synthetic material,    -   or a composite material,    -   or an essentially elastomeric material,    -   or a material behaving in an essentially hyperelastic way,    -   or at least one of said box or said pin utilizes at least one of        a lining or a cladding or a weld overlay.

External clamps 1170 and/or internal clamps 1180 according to thisinvention depicted on FIG. 11 y and on FIG. 11 z made of non-metallicmaterial, including a plastic material, or a natural material, or asynthetic material, or an elastomeric material, or an hyperelasticmaterial can include reinforcements with fibers, wires, a fiber-mesh ora wire-mesh.

Pitch angles of threads 1120, 1121, 1125 and/or 1126 should be selectedcarefully in the design. Large, close to 90° absolute values of thosepitch angles are more effective in the transfer of torque and lesseffective in the transfer of the axial and bending loads, vice versa forsmall pitch angles approaching 0°.

FIG. 12 depicts schematically a segment of a novel connector combiningthe dog-clutch and the fitted shear pin principles. The high torquetransfer region is located near external (metal) nipple seals 1285 andthe torque bearing protrusions extend partly through the wall thicknessof box 1200 and they match cavities in pin 1210.

Pins 1290 or 1295 are tight fitted in cavities of box 1200 and pin 1210.Pins 1290 can have uniform cylindrical shape or pins 1295 can be of aslightly tapered shape (not shown) that would not be visible on thedrawing, if shown. Optionally, stepped fitted pin design 1291 can beused in various implementations of this invention, as shown on FIG. 12 .Optionally pin segment 1291 and the box region where it is inserted canbe threaded, as designated with annotation 1292 in order to highlightthat option (see also FIG. 18 b ). In a case the stepped fitted shearpin shape is selected, the stepped pin nest, threaded or not threaded,can be located in pin 1210, or it can be located instead in the box 1200part of the connector, if preferred so, without affecting thefunctionality of this invention.

FIG. 13 depicts schematically a segment of a novel connector between box1300 and pin 1310 that combines optionally the dog-clutch and the fittedshear pin principles. The high torque transfer region is located nearinternal (metal) nipple seals 1395 and the torque bearing protrusionsextend partly through the wall thickness of box 1300. Fitted shear pinsare depicted in fully inserted and partly inserted positions 1390 and1391, respectively. Remarks already provided with descriptions of otherdrawings also apply to FIG. 13 .

FIGS. 14 a through 14 e and 15 a through 15 c show novel connectorsdesigned for relatively low design pressures to medium pressures with anobjective to considerably decrease the assembly/disassembly fluidpressures in comparison with those used typically in known Merlin™family connectors. For known connectors the assembly/disassembly fluidpressures increase with the reduction of connector size—lower hydraulicpressures are used for larger diameter connectors. For example for aknown, high pressure production riser Merlin™ family connector havingOD=8.625″ (219.1 mm) the assembly/disassembly fluid pressure required istypically very high. The novel connector designs shown in FIGS. 14 athrough 14 e and 15 a through 15 c have considerably smaller ODs than isthe 8.625″ regarded at present as the minimum feasible for the designsof known Merlin™ family connectors. In spite of the above, thanks to thedesign modifications introduced it was possible to considerably reducethe assembly/disassembly pressures required, to the extent that it mayeven be practicable to use compressed gas as the assembly/disassemblyfluid. At the same time it was possible to achieve the overall length ofthe connectors assembled between the weld necks, as shown on FIGS. 14 aand 15 a of the order of 75% of the tubing (piping) OD. The overlapsbetween the boxes and the pins were around 60% of the ODs of the tubing(piping). Depending on the design loading of novel connectors featuringsimilar geometries it may be feasible to decrease the numbers and thepitch of threads used, etc., which may allow to reduce the length to ODsratios and the overlap to ODs ratios even further.

The structural stiffenings of novel connectors shown on FIGS. 14 athrough 14 e and 15 a through 15 c are represented schematically asinfinitesimally thin shells for clarity of geometries shown.Simultaneously with the achievements highlighted in the paragraph aboveconsiderable material and weigh savings were achieved, which may beadvantageous in some applications.

Novel connectors shown on FIGS. 14 a through 14 e and 15 a through 15 ccan be built conventionally (traditionally) by welding the stiffeners tothe box and the pin, subdividing the fairing plate/screen into smallerpanels and welding those to the webs. The hatchings through themid-thicknesses of those meridionally-planar stiffeners 1431, 1432 shownin cross-sections are hatched as traditionally fabricated components.The preferred manufacturing method of novel connectors and theircomponents shown in FIGS. 14 a through 14 e is 3D printing. In a casepin 1410 had been built using 3D printing, the hatchings of stiffeners1431 and 1432 would have been the same as that of pin 1410.

Novel structural modifications introduced on FIGS. 14 a through 14 e and15 a through 15 c are the following:

-   -   Novel variations in the stress IDs 1411, 1511, tapering of the        stress ODs 1415, 1515 of boxes 1400, 1500, or their        approximations;    -   Optional tapering of the inside (stress) diameters 1417 of pin        1410, or its approximation;    -   Providing optional planar ribs 1421, 1521 and/or curved ribs        1523, 1524, 1525, optionally forming stiffening patterns like        for example helicoidal pattern 1526, box pattern 1527 or        honeycomb pattern 1528 on boxes 1400, 1500;    -   Providing optional planar ribs 1431, 1432, 1433, 1434, 1435,        1436, 1437, 1438, 1439, 1440, 1441 and/or curved ribs 1455,        1456, 1457, optionally forming stiffening patterns like for        example helicoidal patterns 1460, box pattern 1461, honeycomb        patterns 1462, 1463 or other patterns 1464, 1465, 1466, 1467 on        pin 1410;    -   Introducing optional web stiffeners 1802, see also examples of        other web stiffener arrangements feasible 1801, 1803, 1804,        1805, 1806 and 1807, see FIG. 18 a . Web stiffener 1801 shown is        double-sided, stiffeners 1802 through 1807 are shown as        single-sided for the sake of examples only. A use of similar        double sided web stiffeners or any other shapes meeting        particular design objectives is also feasible.    -   Fairing the IDs of the pins to constant design values with        optional fairing plates or screens 1471, 1472, 1473 and 1474;    -   Introducing stress relieving cut-outs 1481, 1482 and similar        (shown, but not annotated) that also allow fluid flow across        stiffeners;    -   Adjusting distances between the ends of the threaded segments        and inside and outside nipple seals in order to control the        meridional bending stiffnesses of pins and boxes in those        regions.

Optionally, but preferably in most cases cylindrical fairing plates1471, 1472, 1473, 1474 can be provided with pressure equalizing holes,slots screens, etc., so that the fluid pressures are substantially thesame in the flow and in the cavities formed by pin stiffeners andfairings. Design details can vary considerably depending on the fluidtransported and wide ranges of design conditions. In particular pressureequalizing holes 1491 shown on FIGS. 15 a and 15 b may be suitable fortubing or piping connectors transporting gases with not too big flowtransients. High pressure, flow and thermal transients, multiphase flow,a presence of solid sediments, draining requirements, etc. may requiremore and larger holes, slots or screens with wide ranges of solidityratios. Hole or slot structural or thermal reinforcements like forexample 1817 (FIG. 18 b ) may be required in cases of high pressure,flow and/or thermal transients.

For slender connector designs where reducing component weight isimportant the design of inside (and outside) nipple seal regions mayrequire novel local connector wall thickness increase(s) near one orboth ends like that depicted on FIG. 14 a as 1403. External and internalstructural reinforcements can be used in order to provide acceptableload paths, to optimize hoop stress loading, meridional bendingstiffness and to prevent buckling during the assembly and/or inoperation. Stiffening means arranged on the outside surface of said boxcan optionally include implementations featuring fiber reinforcedplastic stiffenings of said box of said mechanical connector.

FIGS. 14 a through 14 d, 15 b and 15 c show for sake of examples singlerows of honeycombs and/or box stiffeners. However, many more rows ofsandwich stiffeners like those (in particular honeycombs of relativelysmaller dimensions) could be used instead in their places, as it isoften practiced in engineering. The webs corresponding would be moreslender, the resulting straining of boxes and pins would be more uniformand even greater weight savings might result. The single row ‘sandwich’stiffeners in FIGS. 14 a through 14 d, 15 b and 15 c are shown hereinfor example, because those are less typical in sandwich panelengineering. External sandwich panel fairings on box stiffeners (notshown) can be also used. All the above mentioned stiffener designs canalso be used on novel high pressure connectors like those shown in FIGS.16 and 17 .

FIG. 16 depicts an example detail of a novel connector designed forrelatively high design pressures and limited space available along theconnector axis. The design shown features outside tubing or pipingdiameter considerably smaller than OD=8.625″ (219.1 mm). The ratio ofthe length of the connector assembled (between the weld necks, as shown)to the outside diameter of the tubing is just above 60% and the ratio ofthe box/pin overlap to the outside tubing diameter is around 40%. Again,with further design optimizations, a reduced number of threads, asmaller thread pitch, smaller heights of the thread teeth, etc. asgoverned by a particular design premise achieving even smaller lengthand overlap ratios might be achievable. The materials used for novelconnectors featured herein, and in particular for those depicted onFIGS. 14 a through 17 are also of importance. The use of very highstrength materials, in particular where their elastic moduli are notvery high may also help in achieving very high design parameters ofnovel connectors at relatively small piping or tubing diameters (forexample titanium and some nickel based alloys). Because of the highdesign pressure and the objectives to minimize the overall and box/pinoverlap lengths the assembly/disassembly pressure required is relativelyhigh, consistent with those used in the known Merlin™ family connectortechnology.

Box 1600 features multiple tapers 1615 on its outside diameter andmeridional ribs 1621. More complex rib patterns like those shown onFIGS. 15 a through 15 c and highlighted in a discussion correspondingcan be also used, if required. Pin 1610 features inside (stress)diameter tapering 1617 or its approximation, and inside diameter fairingor screen 1671. Fairing 1671 can be optionally provided on the inside ofpin 1610 with pressure equalizing holes or slots (not shown) in order toequalize pressure between the tubing (piping) and pin cavity 1675. Theoptional pressure equalizing holes or slots are required for mostdesigns.

All the connector components shown are represented as solids on FIG. 16. This connector can be constructed using conventional technology or 3Dprinting. A printed connector is shown on FIG. 16 .

FIG. 17 depicts an example of a novel HP connector design featuringaxisymmetric threads and shear fitted pins 1790, 1795 are arranged intwo staggered rows near the outside metal (nipple) seals. Basic designof the novel connector shown on FIG. 17 is similar to that shown on FIG.16 . Fairing 1775 is provided for sake of an example on an outside ofbox 1700. Fairings could be similarly provided on the outside of boxesshown on FIGS. 14 a, 15 a through 15 c and/or on FIG. 16 as well as onan outside of a box of any novel connector introduced herein.

Pins 1790 or 1795 are tight fitted in cavities of box 1700 and pin 1710.Pins 1790 can have uniform cylindrical shape or pins 1795 can have aslightly tapered shape (not shown) that would not be visible on thedrawing, if shown. Stepped fitted pin design is used in variousimplementations of this invention, as shown on FIG. 17 , but a use ofnot-stepped pins is also feasible. Optionally, pin segment and the boxregion where it is inserted can be threaded, see 1792 on FIG. 18 b . Ina case the stepped fitted shear pin shape is selected, the stepped pinnest, threaded or not threaded, can be located in pin 1710, or it can belocated instead in the box 1700, if preferred so, without affecting thefunctionality of this invention. Allen wrench (key) nest 1797 can beprovided, see FIG. 18 b, screwdriver slot, Phillips or torx nest, etc.can be used instead. All the connector components shown are representedas solids on FIG. 16 . This connector can be constructed usingconventional technology or 3D printing. A printed connector is shown onFIG. 17 .

FIGS. 18 a through 18 c depict example design details of novelconnectors.

FIG. 18 a depicts several examples of web stiffeners that can be used atany location on any stiffener on novel connectors described herein.Stiffener examples are shown schematically as shells and they aremounted on a demonstration web 1808. Stiffener 1801 is a double sidedstiffener, stiffener 1801 is a similar single-sided stiffener. Any otherweb stiffeners, shown or not shown can be single-sided or double-sided.Other examples shown are angle stiffener 1803, T-stiffener 1804, bulbplate stiffener 1805 (with the bulb shown as a solid component),undercut stiffener 1806 and double-undercut stiffener 1807.

FIG. 18 b shows equalizing hole reinforcing ring 1817 and example fittedpins 1790 and 1795, which are described in the description of FIG. 17 .Reinforcing ring 1817 can be used to strengthen a fairing plate or ascreen in a case of pressure transients or/and it can be requiredbecause of pressure transients associated with high thermal transients.The materials used can be metallic or non-metallic (tungsten, cementedcarbides, crystals like corundum, beryllium, diamond for non-oxidizingflows, etc.).

FIG. 18 c depicts an example of a typical axisymmetric thread used onboxes 1800 and/or pins 1810, but it is also a relevant illustrationregarding left-handed and/or right-handed threads, see further below.Thread generatrix 1820 is that on the loaded side of the thread on box1800 and thread generatrix 1830 is that on the unloaded side of thetooth. The loaded sides are those that resist disassembly of aconnector. Angle θ2_(b) is measured between the normal to the box orconnector axis (coinciding) and generatrix 1820. Angle θ1_(b) ismeasured between the normal to the box or connector axis (coinciding)and generatrix 1830. Thread generatrix 1840 is that on the loaded sideof the thread on pin 1810 and thread generatrix 1850 is that on theunloaded side of the tooth. Angle θ2_(p) is measured between the normalto the pin or connector (coinciding) axis and generatrix 1840. Angleθ1_(p) is measured between the normal to the pin or connector axis(again coinciding) and generatrix 1850. Angles θ2_(b) and θ2_(p) aretypically greater than zero (preferably approximately halves of anglesθ1_(b) and θ1_(p)), even though designs with angles θ2_(b) and θ2_(p)equal to or close to zero have been used. Angles θ2_(b) and θ2_(p) closeto zero are superior structurally, but connectors featuring such anglescan be very difficult or impossible to disassemble; assembling them canbe difficult too. Known connectors typically use θ2_(b)=θ2_(p) andθ1_(b)=θ1_(p), which can also be the case in novel connectors. However,in many design cases novel connectors use mismatching thread angles thatis to say θ2_(b)≠θ2_(p) and/or θ1_(b)≠θ1_(p), see FIG. 19 . Themanufacturing tolerances on thread angles θ1_(b), θ1_(p), θ2_(b) andθ2_(p) required should be very small (high accuracy required), and eachfew hundreds of a degree of thread angle mismatch makes a noticeabledifference in thread tooth loading when an accurate Finite ElementAnalysis (FEA) is carried out. Therefore, conservatively connectors canbe regarded as utilizing novel generatrix angle mismatches when any ofthe absolute values of mismatch angle |Δθ2|=|θ2_(b)−θ2_(b)| or that ofmismatch angle |Δθ1|=|θ1_(b)−θ1_(b)| is not smaller than 0.02°, butsmaller or larger values like for example 0.01°, 0.02°, 0.05°, 0.075°,0.1°, 0.125°, 0.15°, 0.175°, 0.2°, 0.25°, etc. . . . or even more than0.35° can be selected for the above purpose.

The types of mechanical connectors of long torsional and bending fatiguelife provided with tapering outside diameters of boxes with optionaltapering inside diameters of pins or/and optional radial ribs areimmaterial, all connectors described or/and disclosed herein can beprovided with variable outside stress diameters of boxes, variablestress inside diameters of pins or/and optional ribs. In addition to theconnectors similar to those depicted those shown on FIGS. 14 a , 16 and17 connectors depicted on FIGS. 1 through 11 y can be also provided withvariable outside diameters of the boxes, tapered outside stressdiameters of boxes (or their approximations), with optional variable ortapered inside stress diameters of pins (or their approximations) or/andoptional ribs. The said novel variations and/or tapering of stressdiameters are not limited to those depicted on FIGS. 14 a through 17. Inparticular the taper angles can vary along the boxes and/or pins inorder to provide hoop stress and meridional bending flexibilitydistributions along of the boxes and/or pins optimal for any particularapplication examples shown on FIGS. 14 a through 17 were selectedbecause they feature meeting design requirements that tend to fall ontechnically demanding sides.

FIG. 19 depicts schematically a detail of a cross section of interactingthreads of box 1900 and pin 1910. Optional tooth crest geometrymodifications that result in interference fit are shown exaggerated.

The typical radial interference fit between box 1900 and pin 1910results in normal contact pressures between tooth surfaces 1920 and 1950of pin 1910 as well as 1930 and 1950 of box 1900, respectively. Asalready highlighted above, the above mentioned radial interference fitsare illustrated in exaggeration on FIG. 19 , with the thread sideannotations indicated respectively. Thus, FIG. 19 illustrates inexaggeration the interference fit of the unloaded sides 1920 of the pinand 1930 of the box and it also illustrates in exaggeration interferencefit between the loaded sides 1950 of the pin and 1940 of the box.

In addition to the ‘regular’ radial interference fit of the thread, adesign of additional, superimposed interference fits as illustratedschematically on FIG. 19 is preferably carried out so that the materialstressing of box 1900 and pin 1910 remains essentially in the elasticrange. For axisymmetric threads, thread mismatch angles Δθ1 and Δθ2 arein the meridional planes of the connectors, as shown in exaggeration onFIG. 19 . For threads featuring non-zero pitch angle values, threadmismatch angles Δθ1 and Δθ2 are defined analogously to the above, butthe thread mismatch angles are measured in planes normal to crest linesof the threads. Using generatrices on unloaded and loaded sides of teethwhile defining the above angles assures that those angles are alwaysmeasured in planes normal to crest lines of the threads. With a novelthread mismatch angle between the generatrix of surface 1920 and thegeneratrix of surface 1930 Δθ1>0, an increase of normal contact pressurenear tip 1970 of tooth of the thread on pin 1910 results in comparisonwith the corresponding normal contact pressure distributions in knowndesigns, i.e. those featuring the radial interference fit only. With anovel thread mismatch angle between the generatrix of surface 1940 andthe generatrix of surface 1950 Δθ2>0, additional increase of normalcontact pressure near tip 1970 along other parts of surfaces 1920, 1930,1940 and 1950 result. Whenever thread mismatch angle Δθ2 is greater thanapproximately thread mismatch angle Δθ1 the interference fit resultsalso in bending and shear of tooth of pin 1910 that is defined bysurfaces 1930, 1950 and tooth tip 1970. With slim designs of pin teeththe said bending may also be effective whenever thread mismatch angleΔθ1≈0, or is negative (under the absolute value symbol). Axialinterference fit between surfaces 1940 and 1950 against interference fitbetween the outside contact abutment surfaces is therefore affected bythe said radial interference fits. Essentially elastic bending of teethinteracting results in more even axial and/or bending load distributionsalong connectors than those that would have taken place for anglesΔθ1=Δθ2=0 due to the resultant decrease in the spring stiffness of thethreads. This effect is more pronounced for ‘slim teeth’ threads (andrelatively small axial spacing), than it would be for threads utilizinga greater axial spacing. FIG. 19 illustrates teeth interactiongeometries featuring essentially rectilinear generatrices of contactsurfaces 1920, 1930, 1940 and 1950, however in general cases some or allof the said generatrices can be curvilinear for more accurate control ofnormal contact pressure distributions along the contact surfaces.

It is well known that end teeth take most of the loading on threadedconnections. For novel connectors designs featuring relatively smallerdesign pressures, smaller axial loads and/or smaller bending loads thanthose typically specified for connectors used on production risersoffshore, using less thread teeth may be acceptable. Thread anglemismatching results in improved, more uniform thread loading along theconnector. That is because of the smaller spring constant of a smalleraxial spacing, slimmer teeth. Denser grouping of greater axial spacingteeth near the ends of the thread helps additionally, because of greaterspring stiffnesses of those teeth than are those of a regular axialspacing teeth. In such arrangements more of the load of the regular endteeth is transferred to nearby teeth featuring increased axial spacing,see the thread on pin 1810, FIG. 18 c , where only 3 ‘slim’ teeth areused between the end ‘thick’ tooth and the next ‘thick’ tooth. Similarapproach was utilized in the designs shown on FIG. 14 a, 15 a through 15c , 16 and 17, in all cases on both thread ends.

Maximum contact pressures in regions of pin tooth tip 1970 increase theeffectiveness of leak prevention along the surfaces interacting of box1900 and pin 1910. In cases where temperature gradients exist along theconnector, heat transfer coefficient (according to the Fourier Law)across the contact surfaces is higher where higher contact pressuresoccur. Other important factors affecting the heat transfer are forexample the roughness and the waviness of the contact surfaces as wellas film heat transfer coefficients (conduction, convection andradiation, whichever applies) of fluids, vacuum (or solids, see FIG. 20) filling voids and gaps between the contact surfaces.

Whenever the tooth crest shape modification principle illustrated onFIG. 19 is reversed (increased contact pressures in the region of boxtips 1960, not shown on drawings) similar crest shape modificationswould have similar positive effect on leak-proofing, but the structuraleffects would be decreased, because there is normally a gap between theinside abutment surfaces. However, the said reversed tooth crest shapemodification principle may enhance heat transfer between pins and boxesin installations where connector pins 1910 tend to be hotter thanconnector boxes 1900.

FIG. 20 depicts a detail of connector box 2000 interacting with pin 2010featuring a novel use of assembly/disassembly fluid 2025 solidified incavities. According to one implementation of this principle, after anassembly at an elevated temperature with the assembly/disassembly fluidliquid (molten if it is metallic), the connector is cooled in acontrolled way, so that the desired excess of assembly/disassembly fluidis removed, after which plugs 2015 are inserted into the fluid outletports and fluid inlet port(s) is (are) also plugged allowing theremaining fluid to solidify in all the voids during a controlledcooling. According to another implementation of this principle theassembly temperature may not need to be elevated and instead of anessentially liquid (or molten) assembly/disassembly fluid, a polymericresin freshly mixed with a hardener, and/or accelerator, and/orcatalyst(s), etc. can be used. After the box and the pin are fullytelescoped together, the excess of the assembly/disassembly fluid isremoved, the resin remaining is allowed to polymerize, thus also formingan essentially solid seal. Many resins, including some epoxy resins canbe subsequently optionally re-liquefied by heating up for optionaldisassemblies and pressurized at elevated temperatures for the purposeof disassembling. Glass Transition Temperature of a polymer used versusthe design temperature range of a connector needs to be taken intoaccount. Whichever implementation is used, axial and bending loadcycling can be optionally used after the assemblies during the fluidsolidification stage.

For all novel connectors, and in particular for those featuring lighterdesigns, care should be taken to make sure that the design properlyaddresses and prevents occurrence of buckling in all the modes bucklingcould potentially occur. That is in particular important during theassembly/disassembly and in operation. Buckling potential remains oftenunidentified during finite element analyses (FEAs), and otherestablished engineering methods are used instead. For novel connectorsone can mention for example cardioidal buckling of pin, bellows-modebuckling of pins and/or boxes, shell buckling and/or stiffenerweb-buckling of optional fins. Those may be caused by theassembly/disassembly fluid pressure and/or by combinations of loadsunder various loading scenarios.

Suitable safety measures must be applied at all times, while taking intoaccount that considerable potential energy can be stored in theconnector system during operations, during assembly and disassembly, andparticularly so whenever highly compressed gas is used.

High torsional capacity arrangements can involve a single set of meanslimited to one connector region or any of the high torsional loadcapacity means can be mixed in the design of any particular connector.It is not practical to depict on drawings all the implementations ofthis invention involving all novel combinations of configurationsfeasible, accordingly FIGS. 1 through 20 should be treated as examplesonly, selected for the explanation of operational principles of thedesigns under this invention.

Newly designed connector elements should be dimensioned for specificdesign requirements. In particular some novel connectors require highstatic and fatigue torsional and bending capacities of the same order,while for example their design axial load capacities may be a great dealsmaller than are those typical of the applications of the Merlin™ familyconnectors. In such cases novel connectors may require smaller numbersof threads similar to those shown herein as 160, 165, 350, 355, 1140,etc., and the teeth profiles used may be ‘slimmer’. The designs of suchnovel connectors may turn up to be more compact than are typically thoseused in Merlin™ family connectors used on a pipe of the same size.Stress analyses, design testing required, etc. are similar to thosetypically used in designing and qualifying known Merlin™ familyconnectors, with torsional load related considerations added. Wheneverthermal loading is involved, including transients, the testing programsmay need to be extended accordingly. The teeth designed to carrypredominantly torsional loads or predominantly bending may have moresymmetrical profiles than are those that carry axial, bending and axialpre-stressing loads, because typical loadcases of novel connectors mayinvolve reversible torsional loads (i.e. clockwise and anticlockwise)and reversible bending loads (i.e. left and right in plane, and left andright out-of-plane) of say an adjacent elbow, while negative andpositive load amplitudes are often similar.

For many novel implementations it is recommended to use a carefullyselected torsional preload of interacting surfaces, which in particularcan be achieved by means of radial preload which results in a desiredcircumferential fit between the surfaces interacting. The use of asuitable torsional preload is preferable for similar reasons as arethose with regard to the axial and bending loading of traditionalMerlin™ family connectors, which is obvious to anybody skilled in theart. For the same reason, whenever a close to 90° pitch angle groovingis used, or splines are used, providing such connectors with optionalexternal ribs that would stiffen the connector in meridional bendingmight be considered in the design optimization. Increasing meridionalbending stiffness of a connector by means of meridional ribs hardlyaffects its bulk torsional flexibility. For the same reason splines maybe often preferred to high pitch angle threads 1120, 1121.

It is noted that the description and figures included herein do notlimit the design range of the novel connectors to only those solutionsdepicted on drawings and/or discussed explicitly. The discussion andfigures included herein characterize whole classes and families of novelconnectors with only some specific representations shown as outlineexamples characterizing broader classes of novel connectors.

For example novel connectors utilizing fitted pins many other but shownshapes of fitted pins used in mechanical engineering (including thosehaving for example square or hexagonal cross-sections) that are suitablefor torque transfer according to this invention, can be also used totransfer torsional loads while being arranged between other box and pinsurfaces, not shown on FIGS. 5, 6, 17 and 18 b. For example, somedesigns of novel connectors may be suitable for placing fitted pin rowsin the cavities of the (metal) nipple seals, like those shown as 140, atthe end of a box, at the end of a pin or in both those locations, seeFIGS. 12 and 13 . Fitted pins can also be used between dog-clutch teeth780, 706, 716, 990, 906, 916, etc. All such families of connectorsfeasible are hereby regarded as novel connectors. Connectors featuringother grooving patterns than are those shown on FIG. 11 a through 11 xor on other figures herein are also regarded as connectors according tothis invention.

Dog-clutch teeth can also be arranged at the ends of (metal) nippleseals, like those shown as 140, again at either one or at both connectorends, see FIGS. 11 n, 11 p, 11 r, 11 w, 11 x, 11 y , 12 and 13.

Novel connectors can be welded to the ends of pipes to be connected, orthe pins and the boxes forming a connector can be shaped in the actualpipe material used. Typically high yield strength and small grain highquality materials are used for manufacturing novel connectors.Components of novel connectors can be built from materials compatiblewith sweet or sour service requirements; they can be clad or lined,etc., as the design needs require. Those include boxes and/or pinsand/or other components used in the same connector being made ofdifferent materials. Boxes and/or pins and or/other components used inthe same connector can utilize or not utilize weld overlay(s), liningand/or cladding as required. CRAs, titanium alloys, aluminum alloys,magnesium alloys, nickel based alloys, steels and other alloys can beused depending on the design needs. Conventional or novel weldingtechniques, like for example friction welding and 3D printing can beused. Molding or injection molding can also be used with many metals oralloys (example aluminum alloys).

During the design multiple considerations should be taken into account,in order to provide novel connectors with high fatigue strength. Inparticular the accuracy of finish of the surfaces of the connector isimportant for pre-stressing and for high fatigue load applications. Itis recommended in particular that novel connectors be built to highdegree of accuracy and very smooth surface finish. It is recommended toconsider carrying out shot peening, laser peening or equivalent duringthe manufacturing operations. High accuracy grinding and polishingshould also be used, or at least considered. Benefits of thermaltreatment should also be utilized where applicable, including surfacethermal treatment, nitriding, etc. For small diameter connectorsprecision manufacturing technology should be used.

In cases of crisp separations between the axial-bending and torsionalload capacity areas (for example for dog-clutch, key and spline designs)novel mechanical connectors need to be designed against accidentallocking in a similar way to that, which is used in Merlin™ familyconnectors and/or its third party derivations, see for example U.S. Pat.No. 8,056,940.

Whenever a novel connector has to be assembled at a specific relativeazimuth angle orientation of a pin versus a box, it is optionallyrecommended that external markings are provided to facilitate theassembly with that correct azimuth angle. An optional assembly guidesystem can be provided and it can be designed in varieties of ways. Itcan be removable, or it can be left permanently on the connector in use,etc. Subject to specific design requirements for specific connectors theabove recommendations normally apply to most novel connectors.

Merlin™ family connectors and mechanical connectors of long torsionaland bending fatigue life and other novel connectors have excellentleak-proof capabilities. Metal (nipple) seals at both the inside andoutside diameters feature interference fits, which are very effective insealing. For additional sealing barriers axisymmetric, zero pitch anglethreads can be utilized. They are typically radially, circumferentiallyand axially prestressed. Non-zero pitch angle threads (wherever used) aswell as external abutment surfaces such as 1459, 1659 that areinterference fitted against the thread surfaces normal to the axis ofthe connector can also be utilized. An optional additional sealingbarrier can be added by incorporating O-ring(s) elastomeric or metal,metal C-ring(s), E-ring(s), U-ring(s), etc. in the gap between insideabutment surfaces such as 1457 and/or 1657. The engineer needs to makesure that sufficient draining/exit is provided to remove the excess ofthe assembly/disassembly fluid after the assembly. Special means mayneed to be provided for that, like for example channels connectingthread tooth cavities, additional assembly/disassembly fluidoutlet/inlet ports, if required etc. These may be especially required incases where the threads utilize novel thread angle mismatching describedabove. In particular, it can be noted in the above context thataxisymmetric threads can be utilized to provide very effective extrain-service sealing between boxes and pins of connectors according tothis invention.

Wherever axisymmetric threads are utilized to provide in-servicesealing, it may be beneficial to provide optional check valves or othersimilar arrangements in plugs closing the assembly/disassembly fluidoutlet/inlet ports. Those together with optional fluid capture/removalsystems can be used in a case in service swelling occurs in any sealedcompartment of the annulus between the box and the pin; that can happenbecause of variations in the pressure of fluids transported by theconnector.

In order to improve even further the leak resistance of all connectorsof the types listed herein, in some applications it may be feasible toutilize for assembly and disassembly fluids that would solidify in thedesign range of working temperatures of the said connectors, thusbecoming solid seals, or practically solid seals in cases such as usingnatural or synthetic resins, mastics, or mastics like substances, etc.Assembly/disassembly at elevated temperatures may be utilized for thatpurpose, but that need not necessarily be the case, like for example ina case of using liquid mercury or of sodium-potassium eutectic (NaK) atenvironmental temperatures for connectors operating in low temperaturesincluding cryogenic temperature ranges. The fluids used can benonorganic, organic and in particular metallic.

Care should be taken on the physical, chemical, electro-chemical, toxicand metallographic properties of the solidifying fluids used.

The physical properties include in particular the temperatures andpressures of the triple points of the fluids and their criticalproperties, the boiling temperatures, as well, the temperatures ofrecrystallization as well as the degrees of shrinkage (or otherwise)while solidifying. The chemical properties involve the fluidreactiveness with the connector materials, with the fluids transportedin the pipelines or tubing as well as with other materials used. Thechemical and electro-chemical properties of importance also includecorrosion related aspects. Fluid toxicity can also be of importance. Forexample mercury cannot be used in aeronautical applications that utilizealuminum alloys. The metallographic properties include the subjectivityto diffuse into structural alloys (or other materials used), etc.,(hydrogen induced brittleness, desirable or undesirable nitriding,etc.). One can also mention here phase changes in solid sealants thatoccur with the change of temperature, because of natural changes incrystal structures, of the solubilities of alloyed phases in otheralloyed phases etc., including eutectoidal changes etc.

Ideally the fluid used would be liquid at the temperature of applicationand would solidify with required shrinking, if any is required at all,and remain solid in the entire range of the design conditions. Thesolidification shrinking, as prescribed may be beneficial, because itmay partly or wholly take care of the need to remove excessassembly/disassembly fluid at the last moments of connector assembly.Such solid seals would fill all the gaps very effectively and work likeO-rings. Also ideally the solid seals would have lower material strengththan that of the connector material, so that they could easily deformplastically under the action of changing loads. The temperature ofrecrystallization would ideally fall below the design operational rangeof temperatures, which would enable unlimited ductility under dynamicloading (example: lead solid seals).

For applications where it could be difficult or impossible to find afluid/solid substance meeting all the above criteria, the work below thetemperatures of recrystallization may be acceptable in someapplications, in particular when the solid seal material is temporarilyheated above its temperature of recrystallization. Phase changes due todifferent phase equilibriums with temperature (like for exampleeutectoidal transitions) can have similar effect in lieu ofrecrystallization. Alloys where transitions like that take place andalso other alloys should be examined thoroughly in order to make surethat no hardening like phenomena that could be unacceptable take placeno undesirable phases be formed, etc. Also in some applications it maybe acceptable to allow temporary melting of the sealing material in thedesign temperature ranges followed by re-solidification. In cases wherethe liquid material can boil, extreme care would be required in order tomake sure that the vapors do not cause cavitation damage or otherstructural damage as well as that the subsequent re-solidificationhappens slowly enough to evenly re-distribute the seal material when itremains liquid, and not to upset the connecting functions of theconnector. It is preferred to avoid boiling in the design temperatureranges. Just in case, fluid inlet and outlet plugs can be provided withpressure overload safety valves.

For applications in the environmental ranges of working temperaturessealing materials also used as primary coolant in nuclear reactors canbe considered. Those include mercury, lead, lead-bismuth eutectic,sodium, potassium, sodium-potassium eutectic (NaK). Other materialsinclude for example aluminum, aluminum alloys, copper, copper alloysincluding bronzes and brasses, lithium, lithium-sodium eutectic, tin,bismuth, zinc, magnesium, low melting (fusible) alloys like Rose'smetal, Wood's metal, Field's metal, Darcet's alloy, safe metal, Low 117,Low 136, bend metal, Mellotte's metal, matrix metal, base metal, trumetal, cast metal, etc. Other known metals and alloys, in particularbinary, ternary, etc. eutectics specially designed for particular designconditions can be also used. For example a feasibility of formations ofbinary lithium-potassium and ternary lithium-sodium-potassium eutecticscan be investigated, and if feasible, their properties can beinvestigated and evaluated for use as liquid/(metal) nipple seals. Manyof the above listed alloys have melting temperatures considerably belowthe boiling temperature of water, accordingly boiling water or watersteam can be conveniently and economically used during the novelconnector assemblies/disassemblies. Some remain liquid even below thewater ice melting temperature.

The use of metallic or alloyed liquids/solid sealants can be ofparticular benefit where good heat transfer properties are requiredbetween pins and boxes. Many alloys feasible are good solders, and whenapplicable good solder like wetting of connector materials can bedesirable both to improve solid to solid heat transfer and the sealingproperties. Suitable flux substances can be added. Sealant density canbe also of importance, however where the volumes of the sealant aresmall, the sealing and/or conduction benefits may outweigh the increaseof weight of the connector.

INDUSTRIAL APPLICABILITY

Known Merlin™ family connectors are used primarily for connecting tendonand rigid riser, including Steel Catenary Riser (SCR) joints. In thoseapplications tension and bending loads are high, while torsional loadsare very small. Use of Merlin™ family connectors have been at leastsuggested for rigid jumper joints, however such a use would be limitedto those jumper connections that do not see very high torsional loads.Novel connectors are suitable for use in rigid jumpers subject to veryhigh static and fatigue torsional and bending loads. For examplecomplicated three dimensional rigid jumpers are often used in ultradeepwater.

Simple shaped inverted ‘U’ or ‘W-shaped’ rigid jumpers are often used toconnect subsea wellheads with Pipeline End Terminations (PLETs) orPipeline End Manifolds (PLEMs). Those are fitted at ends of subseapipelines that expand thermally in their longitudinal directions. PLETsand PLEMS slide on their mudmats imposing torsional loads on thevertical segments of the jumpers and connectors and bending loads on theremaining segments of those jumpers. Whenever the jumpers are short,high torsional loads must be resisted by the connectors. Novelconnectors are more suitable for the use with inverted ‘U’ and‘W-shaped’ rigid jumpers than are known Merlin™ family connectors, andthey are more economical to use than collet connectors are.

Another class of examples of suitable use of novel connectors are thoserequired for connecting elbows and pipe segments in rigid jumper designsof SCR hang-offs disclosed in U.S. Pat. No. 8,689,882 by Wajnikonis andLeverette. Those inventors state that spools resisting rotationaldeflections of the SCRs are subject to high torsional loads; bendingloads are also mentioned.

Newer riser hang-offs according to WO/2016/191,637 issued as U.S. Pat.Nos. 10,024,121 and 10,240,400 and also granted as British Patent GB2,556,700, all by Wajnikonis ideally require novel connectors. Theseconnectors are typically subjected to even higher static and fatiguetorsional and bending loads than are those experienced in SCR hang-offsaccording to Wajnikonis and Leverette. In the presently discussed newerdesigns, the torsional and bending loads tend to be of the same order ofhigh magnitudes.

In both the older and the newer classes of the said SCR and rigid riserhang-offs the effective tensions are very small, the actual or ‘wall’tensions in those connectors being governed by so called ‘end cap’pressure effects. That implies considerably lower actual or ‘wall’tensions than are those typically experienced by known Merlin™ familyconnectors used for example to connect SCR joints. All the technicalterms used here are used in engineering codes and are familiar to thoseskilled in the art.

Novel connectors can be used to connect pipes made of materials thatcannot be welded together (example steel alloys and titanium alloys) orof other materials that are difficult or impossible to weld. Additionalfields of industrial application may be listed. Because of theirreliability and the extremely low susceptibility to leaks, novelconnectors can be used for piping and pipelines in the chemical, onshoreor offshore cryogenic installations and in the nuclear industry.Depending where known or novel Merlin™ family connectors are used, theadditional level of leak-tightness provided by utilizing external clamps1170 and/or internal clamps 1180 according to this invention depicted onFIG. 11 y and on FIG. 11 z can be important in preventing leaks of GreenHouse Gases (GHGs) and/or vapors and/or their liquid phases. Thoseinclude for example only carbon dioxide CO₂, carbon monoxide CO, naturalgas or methane CH₄, ammonia NH₃, sulphur dioxide H₂S, various nitrogenoxides NO_(x), sulphur oxides SO_(x), a multitude of freon gases, vaporsand/or other refrigeration gases, most of the above either in a gaseousor liquid state. Helium He, nitrogen N₂, hydrogen Hz, halogenic gaseslike fluorine F₂, chlorine Cl₂, bromine Br₂, iodine I₂, astatine At₂,etc. and many other substances can be also carried as internal fluids ingas or liquid phase. External clamps 1170 and/or internal clamps 1180already described can be also utilized with connectors utilized in linesand/or installations containing methanol CH₃OH, ethanol C₂H₅OH, otheralcohols, glycols or glycerins, etc., multiple grades of petroleum oil,petroleum products like all grades of gasoline (petrol), kerosene,jet-fuels, rocket propellants, and many more. These and many othersubstances used universally in everyday life, as well as many substancesused in Chemical Industry (some very exotic) are GHGs and many can beadditionally very harmful to life and/or to the environment. Externalclamps 1170 and/or internal clamps 1180 according to this inventiondepicted on FIG. 11 y and on FIG. 11 z can be used in any industry,including the chemical, oil & gas, steel production, cement productionand Nuclear Industry in order to increase reliability of connectors withregard to a possibility of toxic, greenhouse and/or radioactive leaks.The remainder of an assembly/disassembly fluid can be left in theconnector or replaced with other substances including fluids or solids(note above and Parent application Ser. No. 15/782,835) in which thetransported substances do not dissolve well or through which thetransported substances do not diffuse well. This invention can also bebeneficial by providing more reliable connectors for pipelines crossingenvironmentally critical areas like National Parks, densely populatedareas, etc. External clamps 1170 and/or internal clamps 1180 accordingto this invention depicted on FIG. 11 y and on FIG. 11 z can be alsobeneficial in preventing leaks of precious water that are considerablein the U.S. and in many other countries. In addition to the abovefeatures, novel connectors have very slim designs and low weights.Accordingly, they also deserve to be considered for aerospaceapplications, in particular cryogenic tubing or piping.

Low cost, high production volumes of connector components used in pipingmade of non-metallic materials, like for example plastics, composites,bonded and unbonded flexible pipe, etc. may be another possible field ofapplication. Large numbers of very accurately dimensioned plastic boxesand pins used in novel connectors can be mass produced for example bycasting or by injection molding. When plastic materials are used,tooling for assembling/disassembling may be low pressure hydraulic orpneumatic.

What is claimed is:
 1. A telescopically assembled mechanical connector provided with a thread on substantially matching essentially frustoconical surfaces of a box and a pin, said substantially matching essentially frustoconical surfaces of said box and said pin extending essentially between two sets of nipple seals, whereas one said set of said nipple seals is located near an end of said box and another said set of said nipple seals is located near an end of said pin and whereas each said set of said nipple seals incorporates axially engaging, substantially cylindrical surfaces with an outside surface and an inside surface of a male substantially cylindrical annular segment interacting radially through a mechanism of a hoop stress with substantially matching surfaces of a substantially cylindrical annular cavity, whereas said sets of said nipple seals are used for sealing a cavity between said box and said pin; whereas said telescopically assembled mechanical connector is assembled and disassembled utilizing a pressure of an assembly/disassembly fluid which expands said box and contracts said pin in a radial direction, which enables an assembly stroke in an axial direction that makes up a connection by engaging said threads of said box and said pin or which enables a disassembly stroke along said axial direction by disengaging said threads of said box and said pin respectively; whereas said threads of said box and said pin can engage only in a correct axial position due to a use of a non-uniform axial spacing of said threads, and whereas an excess of said assembly/disassembly fluid is removed through fluid outlet ports; whereas: said telescopically assembled is defined as being assembled in a telescopic way, being assembled in said telescopic way is defined as having all points of said pin and/or said box substantially follow essentially straight lines during an assembly, whereas said straight lines are essentially parallel to essentially coinciding axes of said pin and of said box; whereas said telescopically assembled mechanical connector includes an at least one mechanical clamp interacting structurally with said box and/or said pin, while remaining essentially unbonded to said box and/or said pin; whereas said mechanical clamp interacting structurally with said box essentially restricts structurally a shell of said box from radial deformations outwards, i.e. away from an axis of said telescopically assembled mechanical connector, and/or said mechanical clamp interacting structurally with said pin essentially restricts structurally a shell of said pin from radial deformations inwards, i.e. towards said axis of said telescopically assembled mechanical connector; whereas said mechanical clamp stabilizes an essentially circular shape of a cross-section of said telescopically assembled mechanical connector by essentially stiffening structurally said box and/or said pin, respectively; whereas said mechanical clamp interacting structurally with said box and/or said pin is installed after said box and said pin are assembled telescopically and said excess of said assembly/disassembly fluid is removed through said fluid outlet ports and said mechanical clamp interacting structurally with said box and/or said pin is removed before said disassembly stroke is started; wherein said telescopically assembled mechanical connector includes at least one of: said mechanical clamp essentially stiffening structurally an outside surface of said box, or said mechanical clamp essentially stiffening structurally an inside surface of said pin.
 2. The telescopically assembled mechanical connector according to claim 1, whereas a term ‘essentially compressive vise grip acting in a radial direction’ is defined as an essentially compressing radially together a female thread surface and a male thread surface interacting with said female thread surface, as if they were engaged in a compressive grip of an imaginary vise; wherein a radial restricting action of the mechanical clamp essentially stiffening structurally the outside surface of the box through a mechanism of radial interference fit and a radial restricting action of the mechanical clamp essentially stiffening structurally the inside surface of the pin through a mechanism of radial interference fit engage the thread provided on the substantially matching essentially frustoconical surfaces of said box and said pin in said essentially compressive vise grip acting in said radial direction at all o'clock locations around a circumference of said box and around a circumference of said pin.
 3. The telescopically assembled mechanical connector according to claim 1, whereas a radial restricting action of the mechanical clamp essentially stiffening structurally the outside surface of the box and a radial restricting action of the mechanical clamp essentially stiffening structurally the inside surface of the pin stabilize essentially circular cross-section shapes of said box and said pin.
 4. The telescopically assembled mechanical connector according to claim 1, whereas at least one of the mechanical clamp essentially stiffening structurally the outside surface of the box and/or the mechanical clamp essentially stiffening structurally the inside surface of the pin is extended axially beyond outside abutment surfaces and/or is extended axially beyond inside abutment surfaces of said telescopically assembled mechanical connector, respectively.
 5. The telescopically assembled mechanical connector according to claim 1, whereas the outside surface of the box is an outside stress diameter surface of said box.
 6. The telescopically assembled mechanical connector according to claim 1, whereas the inside surface of the pin is an inside stress diameter surface of said pin.
 7. The telescopically assembled mechanical connector according to claim 1, whereas the telescopically assembled mechanical connector includes one or more stiffening ribs.
 8. The telescopically assembled mechanical connector according to claim 1, whereas the mechanical clamp includes one or more stiffening ribs.
 9. The telescopically assembled mechanical connector according to claim 1, whereas the mechanical clamp stiffening the outside surface of the box is essentially an annular stiffening clamp.
 10. The telescopically assembled mechanical connector according to claim 1, whereas the mechanical clamp stiffening the inside surface of the pin is essentially an annular stiffening clamp.
 11. The telescopically assembled mechanical connector according to claim 1, whereas at least one of said box or said pin utilizes: friction welding, injection molding, 3-Dimensional printing, traditional welding fabrication.
 12. The telescopically assembled mechanical connector according to claim 1, whereas at least one of said box or said pin is made of at least one of: a high strength steel, or a corrosion resistant alloy, or a titanium alloy, or an aluminum alloy, or a magnesium alloy, or a nickel based alloy, or a non-metallic material including a plastic material, or a non-metallic natural or a non-metallic synthetic material, or an essentially composite material, or an essentially elastomeric material, or a material behaving in an essentially hyperelastic way, or at least one of said box or said pin utilizes at least one of a lining or a cladding or a weld overlay.
 13. The telescopically assembled mechanical connector according to claim 12, wherein the non-metallic material, including the plastic material, or the natural material, or the synthetic material, or the elastomeric material, or the hyperelastic material includes reinforcements with fibers, wires, a fiber-mesh or a wire-mesh.
 14. The telescopically assembled mechanical connector according to claim 1, whereas the mechanical clamp utilizes: friction welding, injection molding, 3-Dimensional printing, traditional welding fabrication.
 15. The telescopically assembled mechanical connector according to claim 1, whereas the mechanical clamp is made of at least one of: a high strength steel, or a corrosion resistant alloy, or a titanium alloy, or an aluminum alloy, or a magnesium alloy, or a nickel based alloy, or a non-metallic material including a plastic material, or a non-metallic natural or a non-metallic synthetic material, or an essentially composite material, or an essentially elastomeric material, or a material behaving in an essentially hyperelastic way, or at least one of said box or said pin utilizes at least one of a lining or a cladding or a weld overlay.
 16. The telescopically assembled mechanical connector according to claim 15, wherein the non-metallic material, including the plastic material, or the natural material, or the synthetic material, or the elastomeric material, or the hyperelastic material includes reinforcements with fibers, wires, a fiber-mesh or a wire-mesh. 